aftermarket pistons can not be installed with out rods for the focus
head work is not needed at all
stock d20 can handle more than the stock auto trans which is the 200whp range
people have different numbers they post b/c there is no set number. like saying that 250whp will not break the engine but 260whp will. any where in the 200's has been done DD on stock engine, but the more you push the power the more you push your luck.
being in the 200's is safe on stock engine with a GOOD TUNE
Turbo Turtle Garage
Zetec and Duratec Turbo kits, engine building