Let me just throw in my novice $0.02... I can totally relate to the cost vs gain issue. It cost me $1500 on new upgrades and about 5 hours of driveway installation time to get my truck to over 550hp and 1100ft-lbs. Granted, the stock platform is a twinturbo diesel, but if I took the same money and put it on the Z, what would the net result be? Not very much apparently. Throw in that the truck is now faster then the Z (though I don't see 155mph in its future) and now I have an unusual tandem. It's just a bummer that forced induction is the way to go to get any significant gains, but so be it. The car is still sweet.
Be on the look out for a 2010 F250 in black with a Yamaha decal out back if you're in SE Georgia. The black smoke is not indicative of a problem... for the truck!