500 bhp will need a little piston work, standard pistons will be ok once machined, but they crack after a lot of abuse, so if your racing I would get uprated ones, boost performance first spec upgraded ones were not good, but I assume they have fixed the issue? or get some FBE forged pistons and do some work on them.

I would just go for a T4 with standard pistons keeping the boost to max 6psi, you should see about 320bhp on a good 24v