Like a turbocharged car, a twin-screw supercharged car doesn't need back pressure. Removing the exhaust back is probably a good idea. For the OP, to point you in a direction, Woody once removed his and ran straight pipes to the back. There's a thread on ehre somewhere and a sound clip of him driving on youtube. If there is any restriction, removing the exhaust will lower the intake manifold pressure. This is however a good thing because the engine is becoming more efficient.




To quote a buddy of mine:

A) NO engine wants backpressure. They want exhaust velocity and scavenging. Backpressure is an unwanted by-product of the first two.
B) The best turbo exhaust is no exhaust. a 6" open pipe the same size as the exhaust on the turbo with no muffler or anything would work best, and thats just there to keep things from hitting the turbine.
C) Centrifugal superchargers(paxton, vortech, novi, etc) like similar exhaust to N/A - but they throw much more exhaust than a N/A motor, so you want bigger pipe all around.
Roots type, which make boost at all RPMs, want no exhaust as well. With a roots, the intake pressure is always greater than the exhaust pressure. It provides its own scavenging effect in that the intake charge blows the exhaust out of the chamber during cam overlap. This is why on blown drag cars they have an individual open pipe for each cylinder(you cant have scavenging with individual pipes). Best flow, least restriction, and built in best scavenging via the blower.

The NA dispute:

i have to disagree with you here...if you're going to be running lower than like 6000 rpms at any point while driving your car, you're going to want back pressure. backpressure is just liek water pressure and air pressure, and not enough of it can slow down your exhaust velocity. think of it like a hose: when you put your finger over it, the water sprays out fast, but not much is getting out, right? this is an example of high back pressure. however, when you let your thumb off, it doesn't come out very fast--and think if you were to increase the size of the tube-it would just trickle out. you need the pressure created by the exhaust to keep a high velocity--but the more exhaust you have coming out (the more power you have) the bigger your exhaust needs to be. All cars need back pressure--even stock cars don't run open headers because they run better with an X-pipe.

The response:

Thats exactly what I said, but backpressure is the by product of exhaust velocity and scavenging, it in itself isn't beneficial in any way. If there was a way to get rid of backpressure and still have scavenging and velocity(like a roots blower for example), that would be ideal. Of course, every car on the road isn't going to be running a roots blower...
Sure you get more velocity with your thumb over the hose, and the water pressure is higher in the hose, but the pump at the other end has to work harder to push it! In an engine, the "pump" is the piston... you don't want to make your pistons work harder, do you? The only reason you make more power with smaller pipes converging into a collector is because the collector provides scavenging, and exhaust velocity contributes to this effect. There is a fine balance between exhaust tubing size and backpressure, too small is too much of a restriction and negates the scavenging gains, too big kills velocity and therefore scavenging. In a perfect world, the piston would push all the exhaust out of the chamber on its own(basically require a 0cc chamber, piston basically hits the chamber...), but we all know that aint possible. In that case, no exhaust would be the best exhaust.