Is it possible to run mid 11's in the 1/4 mile with a 2.5" DP, stock turbo, tuning, and a 3" catback, and test pipe?

 

Doubt it. Most guys are running mid 11s with full 3" exhaust, cams, engine management, upgraded fuel system, intercoolers, boost control, etc. Fastest times I've seen on ANY Evo regardless of turbo is 11.5.

I'd say the setup you speak of might be good for high 12's.

 

YES! If by tuning you mean a Stand Alonene Engine Computer

 

not likely (but anything is possible), your probably gonna need some cams to drop into the mid 11's (more like a low 12's run w/that stuff).