Exhaust Diameter

[boomofdoom88]

So I bought a magnaflow "high flow" downpipe/catalytic convertor. I knew I'd have to cut off part of the downpipe section to fit my headers properly. But low and behold the short section behind the catalytic convertor was only 2 inch. The downpipe was 2.5" I wanted to put a new 2.5 exhaust on my car at some point. Would it be worth my cutting that back part off and fitting a 2.5" outlet to it. or just stick with a 2" exhaust. I'm thinking possibly a rear mount turbo setup in the future. So would that smallish 2" pipe give me a better exhaust velocity? What u guys think? the less welding I have to do/get done the better

Edit: Sorry I didnt specifiy the engine/vehicle Its a 3500 in a Grand Am

[Superdave]

go up to 2.5" and don't look back.