5speed

Given the same brand/model H-pipe on the same exhaust setup, how much difference in sound is there between a catted H-pipe and and o/r H pipe? Also, how much HP do you lose if you go catted? How much HP do you gain by getting a new catted H over stock catted H?

Mark99GT

Off road pipes are louder and sound more raw. Don't really know how else to describe the sound. The power difference between high flow cats and o/r is probably between 3-5hp, not too much. Over stock though, they're probably worth close to 10hp.

If you don't have to worry about emissions go o/r. If emissions are a concern get the catted and get a louder cat back to make up the sound difference (if loud is what you're looking for). Either way an o/r or catted aftermarket H are going to sound better than stock and perform better.

5speed

Great explanation! Thanks for the input! I plan on keeping my stock cat back and I think I am going to go with the catted H-pipe because I want to see some gains, but don't want my exhaust to be too loud. Now I just have to decide what brand. Any suggestions?

Hash06

well even getting the catted h pipe you can still fail emissions

98GTpony

how do you fail with a catted h

MoKo_04GT

i can tell you this much....i dont have any experience what-so-ever with a catted h other than the stock one that came on my 04 GT...BUT....i did put a mac o/r h pipe on there, and i was VERY impressed with both sound and the added power.....the pipe did waaaaay better than i expected it to!! my car now breaks them loose in 2nd just about as good as it does in 1st gear, and the 3rd gear scratch went from a chirp to a bark! very impressive!! i definately reccomend one!! i ordered some cheap *** mil eliminators for $20 shipped (the splice in kind...they are much better/last a lot longer than the plug-n-play) from "mileliminatorsonline.com"...i have no check engine light, they work fine!! my car sounds and performs a lot times better!

Mark99GT

If the cats are functioning properly you wont fail an emissions sniffer or odbII test. Only if it is a visual test and they get you on a technicality would you have a problem. Technically you're not supposed to remove or change the location of factory catalytic converters from a car as long as they are working. I highly doubt you will run into this problem; I've never heard of anyone failing because of it. If your state does the odbII emissions test all you need to do is make sure you don't have any cel codes, which you wouldnt have with a catted mid pipe anyways. Just check and see how your state checks emissions first.

As far as brands, give us a price range and we can better help you out.

redass02gt

you are going about it the wrong way, ESPECIALLY if you care about passing emissions. change the catback and leave the stock midpipe and you will pass emissions 100% of the time, assuming everything works right. emissions is gonna be a crapshoot if you start to f*ck around with the cat converters. there are catbacks which are not insanely loud. I bought magnaflows because I didn't want loud, I just wanted a more aggressive sound. still louder than stock, but not insane loud.

Mark99GT

Yeah, but hes looking for sound AND power. Theres not much if any power to be had with only a catback. Yet you can get both with a midpipe.

PWORLDSTANG

Flowmaster cat back, MAC H Pipe. This combo performs a lot better than stock and sounds GOOD!