Okay - so after reading alot of the old threads about these and the other headers.....it seems if properly done there is 20-40 rwhp to be made with some correctly designed units.
This suprises me 'cause if there was that to be made - I would have throught AMG would have "extracted" that horsepower from the cars in the design phase - maybe I'm elevating AMG too highly...maybe they just knock them out - afterall one of the biggest/strongest drivers for these AMG systems would be the factor note/sound.
Someone with "certified ears" in the AMG stable would come along oneday and go ..."yep - sounds good" and all further design would be frozen in time. Regardless of some more enthusiastic engineers going - but boss we could get another 20rwhp !....but...but...
anyway ....
Long tubes are better for low speed performance, short tubes like these VRP headers I originally posted in #1 are more likely better for high rpm....so drag racing - sure.
In the VRP's there are also Series 1 VRP headers and Series 2. The series 1 ones suffered from a couple of minute but troublesome binding points and - most importantly - some cracking which required welding - but no unfixable.
Long ones are obviously more difficult to fit - but ultimately the more everyday superior option ....
eg:
Dyno-Comp - Blog
I had a read of the wiki -
Exhaust manifold - Wikipedia, the free encyclopedia
may help some newbies.
More than llikely I would suggest to buy these at $1000-1500 if you can fit them yourself - for the stated performance gains when compared to the other $100/hp you spend on coolers and pulleys and the like - it isnt a bad deal.
But - if you ring around and get to know your tuners/manufacturers - there are some smart guys out there that know all there theory and should be able to manufacture a set (like Vlad) but for your specific needs - ie: low or high rpm, and your setup...etc...and extract maximum effect - but it would cost!..I'm guessing >$2000 but you'll probably get a few more hp..... but I'd hazard a guess you would then be thinking about twin pipes and loosing your wheel well in the trunk - but hey - what's important here!
other stuff...
http://www.nightrider.com/biketech/c...austlength.htm
http://www.cobbtuning.com/default.asp