ORIGINAL: MaKaVeLi

i got short headers and o/r xpipe with stock mufflers and have no problems, but if i change my mufflers to flowmasters 40 will i gonna face problem?

ORIGINAL: 97targa

Uhh WRONG!!! 6 cats is correct. They are called "Pre-cats". It's a manipulation technique that Ford used to beat emissions standards to save a few bucks on production costs because cats are expensive to produce! Pre-cats are merely less material and spread out through multiple units. 1996-98's had 6 cats in NY and Cali. Also Newer style Fuel injection cars do not rely on back pressure to run better. In fact the less back pressure the better your car will run! The faster the heat moves away from the port in the cylinder head the cooler the air charge going in will be thus creating more power. The problem that he is incurring is due to the heat! Hot air is no where near as dense as cool air is, ther fore he has less of a charge going into his engine compared to on a cool day. Look at it this way.....A Hot day is like a stock engine and a super cold day with a warm engine is like having a 2psi supercharger added on! Also check your gas that you have. Did you recently put a few bucks in your tank?

ORIGINAL: 2002GTAUTOVERT

wow.. so the MAF, fuel injectors etc. are all useless during the 120 degree days here in august. the engine will compensate for the thinner hotter air. thats like saying in the winter you will run lean and in the summer rich. and the problem isnt with exhaust temperature, its with exhaust pressure. the pressure in your motor is at a different pressure than your exhaust pipe. if for some reason he did something and brought the 2 pressure readings close together.. the exhaust gases wont want to leave his motor.

Also he said he removed some cats and put flows on, no mention of a midpipe... so i dont see how his powerband would be higher. mine didnt change..??

Also he said he removed some cats and put flows on, no mention of a midpipe... so i dont see how his powerband would be higher. mine didnt change..??

ORIGINAL: sstang

I'm just saying what I experienced with my brothers '00 GT. He put on the mid-pipe, and soon after shorty headers. His only other mods before that was an MAC cat-back, JLT intake, and a tune. The mid-pipe made it seem a tad slugish, but not a whole lot to notice. We then put on the BBK shorties and the thing was slow as h*ll until you reach about 45-50 mph, and then it would really wake up. My '03 GT with only a cat-back and intake would spank him from a stop, but from 45-50 mph role he had my *ss all day. From a stop I could probably have around a car and a half on him by the time we reached 50-55 mph. Once we put on the Proffessional Productsthrottle body and C&L plenum, his car would then be able to put a whole car on mine by the time we reach 50-55 mph, and pull even more after that.

While the original poster did not get a new mid-pipe, he did something similar. I wouldn't have thought only removing the cats on his car would do that, but it did. He needs to get the TB/plenum combo for only $200 and see what happens.

I don't think it's the temperature causing this.... unless the temperature went up a whole lot the exact time he cut the cats out...

ORIGINAL: sstang

The headers and mid-pipe were installed correctly. The engine was pulled out a good bit to make sure everything was good. It definitely wasn't a rear end problem, and that would be noticeable. If installing a TB/plenum helped and everything was fine after that,then I don't see how it could have been a mechanical problem. Think about it.