i was wondering if the offroad ypipes actaully do anything hp wise i have a 1990 gmc sierra and it still has the original ypipe brian from tbichips says its a horrible design and is the most restrictive part on the exhaust.I was wondering if i should buy the offroad ypipe and ditch the cat until next inspection would like to get more hp and sound,let me know your opinions.im planning on doing engine work like intake,cam very soon,but i figure i should make the exhaust flowing a little better.I have shorty headers,magnaflow cat,cherry bomb extreme with 2 duals out the back its alittle to quite i think the magnaflow cat has something to do with it.since most of all the magnaflow mufflers and etc are pretty quite on most applacations

 

not 3rd gen related, but yes, most factory y-pipes are rather restrictive, but the factory manifolds are not much better. To see much difference, you would have to change the manifolds and the y-pipe. I now soo you have headers of sort, so forget that part.

keep the cat, but if its original, it wouldn't hurt to put on a new one, or a high flow replacement. It will keep you legal and keep the truck from stinking. wont cost you power to speak of.

 

yea i had a high flow cat on it before and it failed inspection first time i brought it threw inspection with the high cat the hc was 704 then did some adjustments and brought it down to 250 but the nj law is 200 for hc.the only it passed was with the magnaflow cat great cat but it mellowed out the sound alot.ooo well im sure with a nice mild cam it should make it sound alittle better.thanks for you post.