what kind of power increase would i get if i put on a set of e7te heads on my 85 mustang gt. right now i am useing the stock heads (E5TE) i think. my stock heads have some work done to them though, well not much but they have a 3 angle valve job and a set of stainless steel valves. would i notice a big diffrence with the stock e7te,s or not. e7te,s off a 88 0r 89 5.0l gt.