taking everything into consideration (HP, noise, smogging ability, leagality) what are the pros and cons of a downpipe and upgradted cats(or a midpipe, but probably not)? and are the cats worth upgrading or is stock decent? Specifically smog issues in california.

 

Well, as far as smog goes, DP and MP are illegal.

As far as other stuff: if you do both, you'll need to get something to control your boost so you don't overboost. If you get a midpipe, your low end torque will go in the toilet & you'll probably have to do a lot more to keep the boost down (like porting the wastegate among other things).

On the plus side, if you don't have a downpipe, get one. You get a very minor hit in the low end performance side (hardly noticeable) but your underhood temps are so much lower, its difficult to imagine whey they put it there in the first place. Both will give you lots more horsepower (which you'll see on the high end of the rev range). The DP will likely extend the life of your car, and is usually not noticed by the sniffer test or by the people that do the visual inspection on the car.

 

okay so get a DP. should I upgrade the cats too? without getting a midpipe do I still need a boost controller?