PSIfactor is a liar dont beleive anything she says. haha jk. But she did make a good suggestion with the data logger and S-afc. Its a good idea to have your car tuned or ready to tune before you make any major upgrades, you dont want your car to blow up or something. If he doesnt want to do internals yet, i'de still change the head-gasket, and while you got the head off you could do a lot to that, 3-5 angle job, oversized valves, HD valve springs, ARP bolt kit. From there I would do intake if he hasn't. Then I would put in a good clutch i like the 6 puck from ACT personally.
These things aren't really for power, but they will increase the efficiency and longevity of the car before you add serious power. It sucks to just add power and then have something stupid go ya know? things can come down the road are forged pistons, stress-relieved rods, hone or bore the cylinders, open up the oil feed lines, better cams, adjustable cam gears, get your crank shaved and the whole moving essembly balanced. this is when you would worry about fuel delivery, better fuel pump, fuel rails, injector size, throttle body, SS oil feed line to the turbo, ummm i mean the list goes on. Theres a formula that you put in your estimated horsepower and a bunch of other junk and it will tell you the injector size you need, but i forgot it as you can tell.
But as you can tell...it can be a lot of work, not a good idea just to bolt a turbo on, IC, piping and turn up the boost...something bad happens and everyones seen it, its best to build the motor, then you will see a very good size increase in power.
jeff