I'm out of ideas. HELP!

[Gr@nt]

Hey guys, this is my first post.

I got myself a 91 sr5 limited about a month ago and I've been doing lot's of reading on this forum. It ROCKS!

Here's my problem:

It's running on unleaded and LPG. It starts fine and on LPG it drives beautiful, got lots of power but it does backfire on low RPM. 80k's in 5th will backfire. If I use 4th till 90k's then it usually won't.

On unleaded is a different story. It runs, doesn't backfire, but it's got NO power at all. Takes forever to get to 80k's. Can get to 100k's going down a hill, but 5th gear can't even hold that speed with the foot flat.:crybaby:

I done lot's of searching on here and you guys have been very helpful.

We've replaced:
fuel pump, fuel filter, spark plugs, leads, distributor, 02 sensor, timing.

After doing all that, it's actually got a bit more power on LPG, but no change on unleaded.

The car's in good nik and I love it, so if anyone can help me before I :50cal: that would awesome.

Thanks guys

oh and it's the 3vze engine

 

[KidVermicious]

The 3.slow is a dog, but you oughta be able to hold 60 on flat ground.

I don't know anything about LPG, but have you checked your air intake? Engine needs fuel, air, spark, and then compression and timing.

Check your air flow from intake to throttle body.
Verify fuel pressure, and send your injectors for a cleaning.
Make sure you don't have bad gas, I mean, petrol.

Are you throwing any codes?

 

[Gr@nt]

sorry I forgot to mention we've replaced the injectors too.
Air intake is all good.
How do I check the codes?