4-2-1 Headers, Do you think I will gain HP? Options

[Modified]

I have a 94 Celica ST 1.8L. I have stock headers on it now, if I get these headers
Ebay Headers. Do you think I will gain any HP?

[Batman722]

Okay, then it's the need for ANOTHER underbody cat -- the resonator replacement still works for space issues though.
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I don't think I will have any probs with emissions. The non cali 96-97 STs only have the one cat and they pass.

All 94-95 STs are cali emissions, I don't know why. My stock 95 manifold had a crack and I was going to replace with a 97 non cali mani. I got the mani and realized I would of needed the 97 exhaust up to the second cat (different 02 sensors, and b pipe is different). I went with the corolla header and pipe and eliminated the big restrictive first cat and I like it.

If you have a 94-95 and you want more out of your ST then I say do it. I have it installed now and it is different to drive. It is faster, smoother, quicker, better. I am not talking "push you back in your seat" fast but there is a definate noticable improvement. I feel the improvement at all RPMs, no jive. I am not one to drive fast a lot of the time, so I wicked notice it at lower RPMs. Much smoother and faster. Definatly faster off the start and I like it. Its adds a little more "pep" into the car.

overall review, if you have the $$, then do it. Don't expect to start living your life a quarter mile at a time after the install but do expect more responce throughout the RPM band, especially in the 94-95s.