RyanIf the the plastic shims are increasing your spring pre-load then the forks will be stiffer. Suggest you first remove the shims and see how much improvement you get. Do you know the thickness of the shims? 5 or 10mm does makes a difference.
20 to 30 mm is a big adjustment if they were standard springs. They are not shims they spacers!!!!!!Have a look at the pre-load adjustment on your XS750. The max adjustment is about 15 mm!!
Mr. Carlos, it's a shame I don't have my little piston-port MZ* anymore. I would have loved to give you a ride on that one, instantly killing your complains. On a serious note, you may simply want to reconsider your riding mode - one of the things I had to work very, very hard on on the racetrack: On a two-stroke you have to step the gears down until you hit the power-band. Dare to hazard a guess, why I ride a big, tuned V-twin as my daily? *It was tuned for high-rpm, following the MZRC-tuning guide