DT longtubes, DT Y & gibson ss cat back. I used the 90 degree CEL eliminators off ebay with the catalyst in the end, No CEL, not loud unless you mash the loud pedal.

Edit: Just ran a bunch of errands & took my bride to lunch. We both agree it's actually quieter at 55mph than it was before the LT's & Y pipe. The power improvement is very noticable seat of the pants, but there are two rolling hills heading back toward our home that the 4runner normally downshifts to maintain 65mph going up. It didn't today

Any tips here?...my guy in the middle of this job saying he might have to pull the engine to install, get the bolts in/torqued.

WTF?!

Hey guys,

I have a set of the shorty headers I plan to install soon.

For those of you that went with high-flow cats, how is the highway cruising noise? Was it noticeable?

I want to go with HFC's, but concerned that any drone/noise would annoy me on long road trips. Also, I plan to keep my stock exhaust for now.

Thanks in advance!

-Bill

That is really the true test of " did you gain any HP/Torque", something you can measure before/after and "document" improvement as you did.

This thread is amazing. Thanks for all the info gents.

Do you have the part number for this by chance? I'm trying to avoid splicing any eliminators and as previously mentioned the usual o2 bungs seem to be hit or miss.

Has anyone done a header mod in calif?

High Flow Cats won't have a significant effect on the exhaust sound.

If you're keeping your OEM Muffler and resonator, your truck might actually be quieter than it is from the factory.

When I installed my Shorties and GSport cats, I noticed the truck was a bit quieter after the install. I already had my magnaflow catback installed at this point.

My 2005 V8 headers were cracked and leaking and I wasn't sure what route to go for replacement.....OEM.....Doug Thorley......long tube, short tube......aftermarket OEM style..... So I contacted a Doug Thorley dealer and asked them if I could run the 2003-2004 DT long tube headers on my 2005 and that I already had an AIS block plate installed, so I wasn't even using the AIS system.

I get the headers and they look great. After pulling off one of the OEM headers is when I learn the heads themselves have a port for the AIS system. NOT what I expected. I assumed they tapped into the header itself.

So I inspect the DT headers and gasket, and the gasket must work on either AIS heads or non-AIS heads, but the header flange leaves the port in the head open.

I contact the dealer and explain this to them. They gave me the option to exchange them for the 2005-2009 headers....when they get them in....and I pay for shipping the first headers back AND shipping the new headers.

The reason I chose the 2003-2004 DT headers is because they told me they would work.

Now I have to make a decision on what to do:

• Wait for the 2005-2009 headers to come in, and pay shipping TWICE.

• Have plates welded to the headers I have, to block off the ports.

• Drill, tap, plug the AIS ports.

Returning them is out of the question because of their restocking fee.

Thoughts?
Recommendations?

There was a thread I was reading where a guy that was swapping a 2UZ into his Lexus car ended up tapping and plugging the injection ports, so it's possible. That said, the engine was on a stand in his garage.

Thanks. I am not sure I can get all of them while in the vehicle, I am pretty sure I can some of them.

I have several buddies who added this mod and are extremely happy with the results.

Dabsalot, how did this all pan out for you? Reason I ask, I've been looking for anyone that's installed 03-04 longtube headers on an 05+ V8, with an AIP bypass installed. As Inv4drZm mentioned, I'm wondering if anyone's fabbed a block-off plate for the AIPs using 03-04 headers with no AIP tube.

For those that have successfully installed the DT headers, is there a need to reprogram the ECU to understand the new exhaust flow? All of these systems are programmed from Toyota from the factory to work together, so it stands to reason that a significant change the the exhaust system would require an update to the engine mapping. If not, I'd imagine there would be an impact to long term reliability and/or performance.

Please know that I haven't replaced my headers with DT, but with all of the info that I've poured over from a ton of super helpful folks on T4R, I can offer this:

DT longtube headers (deleting upstream cats, connect straight to the Y pipe): you will either need an O2 simulator (URD sometime has one on their website), or space out your downstream 02 sensors with something like this. With LT headers and deleting the upstream cats, can't recall anyone getting around either of these 2 options.

DT shorty headers (keeping and welding either your stock cats, or aftermarket, and then connecting back to the Y pipe): I think some folks still get away with needing no rear 02 sensor trick, but I've paid less attention to shorty installation in reading through posts. I'd imagine it depends on the what cats you're welding back up to the shorties (hi-flow vs OEM-aftermarket).

From what I've read, nothing needs to be done with the upstream 02 sensors, located within the header/manifolds themselves, as they only measure and dictate air to fuel ratios. The 2 downstream 02 sensors read catalytic converter efficiencies, and need to be tricked if any or all of your cats are either old and shot, or completely missing, in the case of installing LT headers.

As I understand it, no tuning is necessary, the ECU will learn and adapt, once, of course, you've taken care of or tricked any 02 issues, if you even need to. There are other folks on here that've had these setups for years that can speak to longevity, and any issues they've come across. Unfortunately, with these trucks & Toyota in general, tuning isn't as simple as hooking up a Cobb AccessPort and throwing an OTS tune on after modding, as I understand it. Of course, if you're moving up to forced induction, that's a good time to get into the tuning game with these engines.

I ended up going with the 05+ Long Tube headers. Probably the best option for my case.

On a related note, I went with the URD O2 simulator and with a little adjusting I was able to eliminate the ‘catalytic converter efficacy’ code. But only since installing the DT headers I sometimes get a P0172 & P0175 code ‘System too rich bank 1 & 2’