Hello all,
Just installed a 4" MBRP with front pipe (now catless) and I get a weird "hissing" noise. Searches came up short so here is my questions.

Do other LLY's have this issue? If so, what is it? I have installed a EGR Blocker and Mr. Fingers goodie. Also running on a preditor 65 tune.

The hissing comes on at idle and only after 10 seconds or so (hot or cold). I cant believe this is turbo fins as it is repeatable and not present at startup. Only after idling for 10+ seconds. What valve is coming on? Is it there a warm up valve? Should I be concerned? Its quite loud.

Thanks in advance
Dave

Hehe... Welcome to the world of the VVT. I installed a 4" MBRP system in my father's 04.5 has the same sound. Only thing I can say is after a few months that loud hissing sound will quiet down some, but never go away.

I'm sure what you are hearing is perfectly normal.

moving to exhaust section.

sound is normal, you have less backpressure now so the sucking and exiting is going out the exhaust.
this is what a diesel sounds like with open exhaust..LLY anyway. If you did the same thing to a gasser you couldn't hear yourself talk.

Thanks!

Humm.. Back presure lower? There must be a valve that comes on (or off) because the noise is not there at start up. I believe we have a warmup valve and that may be what I hear.

Anyway.. Great site.. Thanks again
D-

yes..EGR valve

You might want to check your EGR blocker plate to see if it is leaking. you can tell by the black soot if it is.
mine leaked after i R&R'ed it for a trip to the dealer and got it in crooked. it made a he** of a hissing wistling noise.
after about a week, i looked at it and found the soot around the plate, reinstalled it and no more noise.
I may be off base here as i dont have the full exhaust yet but i do have the cat delet pipe.
just my .02
hope it helps somebody

You took out the kitty...now it is hissing???
I would think it would work the other way!):h