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"Mechanical Considerations: Modern (1987 up) 4 valve/5 valve combustion chambers are generally not prone to detonation for brief excursions to 12 psi. Do not confuse boost psi with airflow in CFM. Turbo nozzle discharge @ 12 psi from a small turbo IS NOT the same as 12 psi from a larger turbo. RB Racing supplies only large CFM turbos that will produce more power at a given level of boost than will less efficient turbos without custom designed compressors. Your modern 16/20 valve engine is designed to breathe in the narrow window of 10,000+ rpm and, as such the effective compression ratio is less than the stated 11.0 to 12.0:1 manufacturer's static compression ratio. When you factor in camshaft duration necessary to allow sufficient inlet/exhaust overlap @ 10,000+ rpm your effective compression is much less. On (1987 up) motors we normally recommend you leave the stock compression/pistons in place. If you are hell-bent on "building" your turbo motor do not lower your static compression ratio below 10.0:1. For camshafts you can increase the valve lift but do not shorten the duration and therefore the overlap of the camshafts. Overlap on a turbo motor prevents overworking the exhaust valve by allowing cooling of the valve to take place which also helps to prevent the onset of detonation. In general the lower the compression ratio the more boost you can run and the more power you can make. If you build a 50 psi. 6.5:1 C.R> motor it will produce a lot of power but be a "dog" everywhere below this. "