what size exhaust tube/elbow etc for my setup?

[CNHSS1]

i currently have a 2.5" system with a single Jetex medium length oval silencer which exits thru rear of passenger door. That runs static at tested rpm 4350(suppossedly 2/3rds of max ) at between 98 and 102Dbs. variance is generally how up to temp engine is and how good the testing equipment is. Ironically although it registers apprx 100Db static, its quieter on track than some of the mildly modified V6s that register 89-96Db. The turbo does a great job of chopping up the sound pulses when under load. Im gonna lag the system from manifold all the way to tail pipe which will help a bit (and stop cooking me!)
Whaddya reckon?