RE: Tuning nightmare
JMO...While the 2.5 cast silver cooling head lacks in cooling perfomance, the 2.5R and 3.3 cooling heads cool just fine.
There would be no differance in the tuning of the engine with either the stock, nova or acncm heads cooling heads.
The only differance would be the cooling efficiency. If you cant keep the temps within operating range with the stock head, you need to tune up your tuning/troubleshooting skills.