I have a 1990 Toyota standard cab 2 wheel drive short bed pick up. It has a 22r with a 4 speed manual transmission.I'm having a surge problem. when the truck is idling, it shakes violently. in third and fourth gear the surging is not noticeable. in first and second gear, if the throttle is held steady, the RPM's Surge up & down terribly. it will do it sitting still Or while driving. I have done a full tune up, changed all the filters and the egr valve. Any ideas?