I finally got a few nice days with out rain and had a great day running my rc's. I made a couple of changes to the GRP.21. I replaced 2 of the standard springs for hard springs on the fioroni clutch and changed from the JP4 pipe to a dynamite 053. Man I cannot believe the difference. My GRP .21 now has great bottom end. I believe the problem I was having before was in the clutch. I built a track on the back of my propert a couple of years ago with a d4 cat and I use it for practice and tuning. At full race speed today I timed 4 full tanks lowest runtime was 11:10 and longest 11:30. Run time was in a Jammin x1x buggy. Engine is now very smooth with enough bottom to pitch it sideways on demand.