were is the best place to by

do I need to change the down pipe

does 4" give more hp

how much hp and mpg can I expect if any?

Thanks for any help

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correction does 5" give more hp

 

all 5 does is make it sound deeper ... as for mpg and horses u wont see much mabye a few. your throttle response will be better. i have a 4 and it is all that is needed

 

5" is only beneficial over 4" when you exceed about 600HP. Until then, there isn't enough airflow to require the 5".

 

5" just sounds better

Luke

 

I would guess the 4" installs easier. Clearance was pretty tight in some spots on the downpipe with mine, I can't imagine how much more of a PITA it would have been if it was 5".

 

I agree JBearSVT I just put a 4" diamond eye turbo back straight pipe on my truck yesterday and I couldn't imagine trying to get a 5" down pipe in that little bit of room. And my 4" sounds good enough for me!

 

It sounds a lot better to me since I put the MBRP muffler on. I mean, it really doesn't sound any different in the cab, but outside it was just retarded.

 

Yep I would have to agree the only difference is sound

 

I have yet to see a company make a 5" downpipe for a 2nd gen truck. Every 5" kit I have installed has a 4" downpipe and then turns into 5" after the downpipe.

 

Well that would certainly make it easier, there's plenty of room everywhere else.
On the other hand, it sounds like the downpipe would be a bottleneck in a 5" system.

Then again, it's coming off a 3" flange from the turbo, so maybe that's a moot point.