going from 2lbs to 4lbs??? Need a new tune???

[VETTEKIL]

is it necessary???

 

[MalcolmV8]

It's possible. You need to datalog and make sure your A/F stays in check and you don't max out your MAF counts, injectors or pumps. If unsure have Mo review a datalog of a pull on the new pulley and go from there.