From my experience, when I drove at 55, I'd actually be pretty close to 63 & when I was at 65 I was closer to 75. This is what I learned using my GPS.

Horse power can be an issue but then again, I think I just don't demand as much acceleration from my truck as most people do.

One thing I gave up on a long time ago (from the beginning actually) was trying to keep up with other cars acceleration rates. It's just not where a Monty excels.

Now that I have my golf (2.0L aka "2.slow") I can get all the speed fix's I require. I can tell you that I'm glad I didn't buy a much faster 16V GTI or a VR6 GTI. I'd probably have a ticket or two by now.