[holman]

I live in the U.S. and I have a 1999 Viggen.I'm going to upgrade the ECU to either a stage 2 or stage 3.Which is the way to go? I'm also going to add a 3" exhaust system,bigger intake tube and a opti-flow air filter.Also why does Abbott only make a 2 1/2" exhaust systme and not a 3" system.

 

[burre]

As for the size of the exhaust, bigger is better on turbo cars, however, 2.5" seems to do a good job on our cars. The bigger difference in exhaust performance seems to be in the cats and the muffler which are much more restrictive to flow than the smaller diameter pipe. As for stage 2 or 3, I can only suggest you do the necessary mods before going for the ECU. You seem to have the idea of freeing up both exhaust and intake flow. Do those mods first and then go for the higher stage. If you go conservative at first, you'll just want more power later.