whats the max hp gain ... without juice or supercharge

also ... r those universal mufflers that sell from 75-125 dollars
good ones... any difference in hp or sound

 

For an 01 the biggest gain is from a Y-pipe (20HP). It works best in conjunction with a Cat-Back and and intake.

 

how much would i expect from a straight pipe?

 

Do you mean a pipe to replace the main cat? ie. test/straight pipe.
If so nothing more than 1-2hp if any.

 

that y pipe number is a tad liberal. 4th gens typically pick up around 15hp from the y pipe alone but they are removing two precats. on 00-01 they only remove and typically pick up anywhere from 10-12hp.

 

how bout those universal mufflers... how much would i expect from those?

 

just a muffler, id say 3hp but if i were you i would stick with a y pipe, b pipe and the oem muffler unless you want a few hp and a good bit more noise. you can always put a larger resonator if you want an aftermarket muffler. i would start with a y and b pipe and you dont really need the stock resonator with the stock muffler on. i dont have one and i barely notice any difference in sound except a little more burble at idle. it would also help to open up the intake side to pull more in.

 

with just the Muffler, I'm sorry there's no gain. If you are lucky you get 1 extra HP. Most are just for show and sound