After doing some reading it seems a good system that has electronic cut-outs gains very little from thee cutouts meaning that it is the good system making the power, cutouts maybe 7-8HP. I've got an idea for an exhaust I think will be good but can't start out with $800. downpipes that I plan on welding a set of cats into anyways. I am hoping for 25whp with the exhaust I have decided to put together. Just can't find a set of downpipes! How about the stock downpipes, anyone know the tubing diameter offhand? I don't want anything larger than 2.5" diameter and would prefer 2.25" to keep the velocity up so the scavenging effect works out well. I am planning on an X-pipe instead of the 2nd set of cats, no resonator and a Borla 400482 Turbo Pro XS muffler. The Borla's do not drone but are loud, the x-pipe should take some of the loudness out. Having a quiet freeflowing exhaust is important to me. It does not seem that there have been before and after dyno tests of many if any systems. I'll do the before and after, just need to have the downpipes reasonably priced. The Borla's also make good low end torque and that is what I'm after. Peak HP on a SC vehicle doesn't mean much as the peak HP is at redline.
Well do I have to go custom, work with the stock pipes or are there downpipes oriced where I can add $300. cats and labor and possibly a second muffler? Mark

 

I asked Rob for a set of aluminized pipes to cut the cost of his quality work but I doubt the change. You guys who have shown little difference with electric cutouts with GOOD catback systems shows there is power to be made with the resonator/muffler area. An X-pipe in place of the rear cats, deleted resonator nd a BORLA #400482 muffler could yield my car 25HP. I am pushing 20+ PSI of boost now so it(the echaust) is something to look into. I am going to take 2 months before i do any other mods so i make the right decision having limited funds to work with and taking time for research and asking questions of the more experienced.
I guess I could work with the stock downpipes or have a set of custom pipes made. I like the quiet of the Mercedes and should try to keep it that way while making those 25 horses lurking, waiting and readying to burst out!
For the guys who have been down this street before any things to go with or those to avoid would be appreciated. Thanks and even weak opinions are needed at this early point in my quest for 25HP from the exhaust change

 

Thanks, I like the 17HP & 18 TQ on a DYNO! What other mods do you have or is the exhaust the first? Obviously the more mods and power before the exhaust should equate to more power and torque after the exhaust mods, very encouraging!

 

Yeah, that is a 2-3 year old post. Jim, if I discounted every old post I might not have the 70mm SC pulley that I do have and love. I'm going to throw this fellows response into my mix of info that will take me about 2 months to make a final decision. I believe an X-pipe makes more power than an H-pipe also, something else to confirm. I datalogged 20.6 PSI this morning and of course higher boost across the rpm range so more exhaust gasses to get out of the motor and exhaust system. Just about 50% more than stock. 42% to be exact, still a bit more spent gasses to expel. Again, a start of 60 days of research and interviews when possible! Mark