Well I am finally around to getting a downpipe. I have the zzp shorty header so I was just going to go with the zzp downpippe with a h/f cat. Before I purchased it , i decided to read the reviews. Well to my suprise, many people are claiming that when you accelerate it is giving a whistling sound. I DONT WANT THAT. So can I get a list of suggestions for downpipes with a high flow cat????cause I am a little bummed.

 

i get a whistling sound with my long tube header and no cat, not sure what causes it, but its there at low rpm when i put on the throttle. Crate Engine Depot has the best downpipe and high flow cat for sale and i believe its made by Random Technology, costs over $400 though.

 

Save yourself some money and get a catless dp. no whistling just louder.

 

i have a ZZP 3" with hf cat and gmpp manifold. no whistle, except from my blower
ZZP is widely recommended, especially their midlength header / dp combo.

 

I have the zzp header/dp combo...my dp is 3" tapering to 2.5" with a high flow cat...I have never heard this whistling sound you are talking about...and I also have 2.5" cat-back as well

 

yeah, i think whistling may come from a small leak in the header or downpipe, i still haven't been able to find where mine comes from cause i took the cat out and it still does it. You probably don't have to worry about it if you bolt everything up correctly on the high flow catted downpipe.

 

no complaints with my random technology downpipe.