I haven't dynoed my car, but I bought my gt40p's off of e-bay, with "1.94/1.54 ss valves, and .600 lift springs(unported,unpolished,non egr) from a place called tri state cylinder head, in Indiana. I paid 569.00 for the heads, and I put them on my engine combo, and ran a 12.7 @107mph n/a I would...