At the time I was only getting 38-40 MPG (that's US gallons) with J-Costa installed. I just wore the poor thing out going everywhere at top speed, all the time, here in Oklahoma.
I was looking on a sight, I think in Germany, that had different weight pins for the J-Costa. That was a while ago.
Here's a site that has a few different weights of pins for the J-Costa. They do make them. Now as far as over all dimenstions????