How much HP/Boost from cat-back exhaust?

If all you are going to do for now is one thing, I would get a downpipe and a BCC.

The two would be cheaper than an exhaust, unless you go used or buy an N1.

Will a downpipe fit the stock exhaust? Still, i'd like to know if anyone has just put on a cat-back system and dyno'd their car. I've been thinking about the Greddy SP, but i'm wondering if it's too quiet (i'd like to hear the straight 6 a little!!).

when my TT was totally stock, i installed a TRD exhaust and i took my car to dyno, i got 310rwhp for the result, without TRD exhaust, i got 298rwhp. Hope this can help

Get the dp first. It will make a much bigger diff than cats and aftermrk exhaust. With a dp and stock exhaust, I could hit 15.3 psi on a cold day. With dp and exhaust, I can hit 17 psi on a cold day.

R5-Turbo said:

Will a downpipe fit the stock exhaust? Still, i'd like to know if anyone has just put on a cat-back system and dyno'd their car. I've been thinking about the Greddy SP, but i'm wondering if it's too quiet (i'd like to hear the straight 6 a little!!).

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I have the SP, you can hear it when you get on it.

Do you guys know if the Blitz or Rod Millen DP will fit the stock exhaust?

I don't know about the Blitz but the standard downpipes like SP engineering, scott performance, Stillen, Rod Millen, etc all bolt up to the turbo exit (EGCV to be specific) and bolt to any cat-back exhaust, and all catback exhausts have the same flange as the stock exhaust for obvious reasons, so of course the stock exhaust will work with any standard Supra downpipe............

Andi

YEP it does. I got ride of my Hiper exhaust cause it was only 2-2.25" diameter inside the length of the muffler. I now have my stock exhaust back on till i get an N1 and it bolts just fine.