A turbo setup for a GSR will cost alot less than $4000. If you peice a kit together, your looking at 1500 - 2000. FI is the absolute best bang for your dollar, end of story. Proven time and time again. And can be completely reliable if you tune it properly.

If you insist on the ITR motor, then just buy it. The B18c5 is a great engine, and an enginering marvel IMO. Just highly over priced because of all the hype. Aftermarket cams will deffinately give you a bit more power, but dont forget to figure in the cost of tunning. Probably another $500, on a conservative street tune. And the cost if upgraded valve springs & retainers to support the higher rev's. And to take full advantage if the higher lift, you'll need to raise the compression a bit. And I deffinately do not recomend pulling the head of a perfectly good ITR, to install a thin head gasket.

I bet after you spend $1500 + on mods for that ITR, you will be dissapointed. You'll hardly notice 20 +/- HP.

When its all said and done, your the one who has to look at it everyday, so do whatever you desire.