Following Sid's observation that the ceramic exhaust ports aid early spool given the long run from the exhaust ports to the turbo hotside - it's got me questioning the trade-offs of a worked NA 8 valve head v the 951 head.

A worked big-valve N/A head can be made to have some exhaust flow advantages over a worked 951 head - but do these more than off-set the loss of exhaust gas energy due to losing the ceramic exhaust ports?

I'm assuming the motor is being run within the stock rpm range - but obviously tuned in every other respect.

Tim