Thats a great response! Thanks very much. I ran across those performance charts today. The (big) reason I asked is that I had a new R4 on the car for two days before it crapped out, and the drivability was terrible. If-thats-what- AC-is-like-I-won't-bother-with-it kind of terrible. Maybe there was something wrong with this compressor, as I had to use a wrench to turn it over. Fortunately, I was able to return it, so that money will now go into a Klima kit. They give you an option between the 5 and 7 cylinder, so I figured I'd ask what the difference is.