Are these worth buying, what sort of HP increase would I get?

It's a stock 350TPI, soon hopefully going to have Headers to cutouts and behind the cut-outs dual hi-flow cats, and true dual exhaust with something like Borla XR-1s (Haven't 100% decided on a muffler yet)


http://www.summitracing.com/parts/EDL-3860/

http://www.summitracing.com/parts/EDL-3865/?rtype=10

 

Without a cam or head change you won't see any difference.

 

well you would let the stock heads breath a little better, but id definetly recommend at least a cam change

 

Alright, I wasn't planning on doing anything too major to the engine right now. I suppose I'll work on my exhaust for now.

 

You will be allowing the engine to breathe a little better with this combo, but as has been said new heads will be a must and a new cam would greatly help as well. And take it from someone who found out a PO left the plenum on his car stock and installed SLP runners. This mod doesn't do a whole lot unless you port match the plenum to the runners.

 

Alright, I won't waste the $800 then lol.

and I know this isn't the right section, but I figure I'd ask you guys instead of wasting a whole new thread, because I'm only slightly curious.

What kind of HP and ET changes would/could I expect to see from Headers running to dual 3" cutouts. (I plan on having a quiet-ish street exhaust system the rest of the way, so I don't care about power when the cutouts are closed)

The exhaust system is completely stock right now including manifolds

 

you're better off doing the exhaust side first. headers, exhaust pipes or cat-back if law requires.

 

$820.00 for just runners and a base.
in my opinion, no they are not worth the price.
what about the plenum and throttle body?
you use the factory pieces with those parts you have listed.
the factory throttle body is good enough for a 350 motor.
like was said, the stock plenum will need some port work, which isn't a big deal if you have the tools and a little know how. you can find the "how to" on this site.

IMO, the FIRST intake is a better deal.
for $1000.00, you get a huge set of runners, a matching base and plenum, throttle body and fuel rails.

the down side with the FIRST, you'll need an after market fuel pressure regulator and you'll need to rework/fab up your fuel lines.
up side to the FIRST, even with professional port work done to those runners and base, they still won't touch an out of the box FIRST.
with port work the FIRST will allow you to expand even farther if needed.