i have an 02 svt focus, and i put a stock 2.0 zetec out of a zx3 and i have a lag at 3500 rpm. would that have to deal with not have the right computer for that engine? how can i fix this??

the only reason why i got a stock 2.0 zetec was because my engine blow and i didnt have the money to get a new svt engine..

Wow... I dont even know where to start.

As for your problem at 3500 it could be because you lost your dual stage intake (assuming you used a zetec intake manifold), or could also be a problem with spark timing or fueling.

the engines are so completely different you really need to go back to an SVT engine or get a computer and wiring harness for the zetec.