here is my take on this:
the front mount turbo will always be more efficient than the rear mount. why? because its the expanding hot exhaust gases that spin the turbo, not simply the volume of it and how fast its coming out (although those two do play a role in it). the rear mount is further away and therefore the exhaust cools down a lot by the time it gets there. the front mount is only a foot or so down stream from the head so the exhaust is still expanding, meaning it will spool faster and create more boost.
the rear mount doesnt need an intercooler because the pressurized air has to travel the length of the car to get where its going. While this is helpful, it also means the turbo has to make more boost than a front mount because it has more pipe to pressurize that a front mount. so a front mounted turbo wouldn't have to work as hard as a rear mounted one would. the intercooler used in front mount applications isnt really that huge of a restriction, and even if it is, the fact that the front mount is more efficient will porvide enough pressure to where the restriction isnt a big deal.
also, I'm not too crazy about running an oil line all the way to the back of the car. I'm sure its shielded, but I'm just not comfortable with it. however, it does create a nice drop in oil temp by the time it gets back there.
the last thing is the price. there are a lot of guys making their own front mount turbo kits with truck manifolds flipped upside down. that obviously makes it a bit cheaper than buying turbo manifolds. but you just cant beat the price and convieniance (sp?) of the sts rear mount setup.
thats my story and I'm sticking to it!
