Hi sorry to butt in again, i built numerous engines and ran the vauxhall pistons pal they sit further down on the gudgen pin dropping the compression by sitting further down the cylinder but people often overlook the under piston oil cooling spray bars which the zetec needs. I have found that when given alot of boost the pistons movement knocks these bars off when you build the engine the clearence between the piston and the cooling bar is minimal, when i have stripped other customers engines down who have come to me saying they have melted number 3 due to fuel and air being wrong its turned out to be no spray bars which will cause the piston to get too hot not the mixture. sorry if i am going on and interfering