Truthfully, before 89 the 325 only had like 132 horses, and when your talking only 4 horses and probably close to an extra 150 pounds for 2 extra cylinders, that's quite a bit. I'm turning probably close to 140 bhp now, with my exhaust and conical filter. I think if you are strictly going from the 85 and 86 stand point, you will see a great difference. I've thought (for about a second) to go to a 91 325is, but I'm getting 31 mpg and still having fun driving it (when I get about 5 miles from my house the road turns into silly string, it's great).