In my 89 240 i cut off the front muffler and straighted it back to the last muffler, where i threw on a glasspack style muffler rather than a baffled one. I thougth it might sound cool but its really starting to piss me off and sound like a fart can honda (the work to install the glasspack and straight pipe along with new tip cost me $85 all together including parts). It creates less backpressure, but not too less ( you still need some with a non turbo )

I've noticed it take away from low end torque but overall power, especially on the highway, has improved slightly.