I've already got the i/e, and I'm looking to get a header and downpipe. I'm wondering if the stock pipe is restrictive enough that a new downpipe would give any noticeable gain?

 

Noticable? I don't know how much... but it's said that the stock Spipe is the most restrictive part of the entire exhaust.

 

Oh also, would it fit with a Borla Catback exhaust? has anyone done this?

 

Most Downpipes should match up no problem... but can't see it do "THAT" much.... the cats and resonators are what slow down everything pretty well.... once you add a header/and catback exhaust, you'd probably not notice a difference with a s-pipe or not....

I'm still on the fence with this one... just don't know if it's THAT big of a deal.

 

Its really not...if you have everything else done, then go ahead and get it. On a stock setup, or with an axleback only, its money better spent on something like an intake, short shifter or an engine damper IMO. Not a badpart, but doesnt offer all that much.

 

If you wanted to do a full exhaust system then get it. I think with headers and cat-back it will give you about a 5hp gain. I'm pretty sure ive seen a ZPI spipe dnyo sheet around here somewhere.