I had a LCE long tube header on my 98 Tacoma. It definitely made the exhaust a little bit louder through the stock muffler. I also love the header sound that you hear under the hood.
As far as performance, it does help but you are only going to notice it in the mid to upper range of rpm. I had my header for 5 years. After repairing it twice(faulty factory welds), it failed for a third time and I said enough. I took it off and re-installed my factory manifold. I was blown away how much lower rpm torque I got back! It made driving the truck much better because you spend most of your time under 4000 rpm unless you like winding it out all the time.
If you are still dead set on a header, I would look in to just doing the late model factory header swap if you have the stock cast manifold. keep the factory setup for the best torque especially if your ride is a heavier 4Runner.
And even then, since you are talking about a motor swap in the future, I would just save your money instead of buying a header.
