I have a new 05 LGT and have recently been kicking myself for getting this exhaust after finding out that it is only a 2.5" exhaust after getting it on my car. My question is, will having only a 2.5" exhaust hurt me when I go to stg 2? In a way it might be ok since it wont be too loud but I really hope this wont be a downfall when it comes to getting more power.

Turbo back or cat-back?

cat back

LGT are dual exhaust not sure if thats from the cat back though from the cat back dual 2.5" might be too big

its not a dual exhaust, its 2.5" back from the cat then it splits off into two mufflers.

As long as you get a 3'' downpipe, it really won't matter.

If you like the way it looks and sounds, keep it. A 2.5'' catback won't perform much worse than a 3'' catback, we're talking like 3-5hp (at most, and not necessarily at peak)

After seeing the design of the y pipe, the stocker looks better.

I've been dissapointed time and time again with the Borla systems both in quality and flow. Both Greddy and Blitz make excellent cat back systems and should be considered prior to purchasing a Borla.

it wasn't a tought decision for me a custom turbo back for 900 or a 700 cat back..

on the other hand you will be fine runnign stage 2

and there ie at least one point in the borla where it is only 2.25