Please do not do that, the stock muffler is very restrictive and has maybe a 2 1/4" inlet. A 3" exhaust to the stock muffler would be pointless and not gain as nearly as much power as it would with a true 3" straight muffler.
Getting rid of the stock ECU would be the first thing on my list. You will be much better off with an AEM standalone.
LSD should be fine... clutch will be on the limit.... and again, be carefull with the boost in higher gears.
