engine starts and runs fine. When cruising for 30 min or so, no problems, when slow down to idle speed (700-1200 rpms) for more than 20 min or more, engine will stall either at that rpm or if I try to increase throttle it will stall . Have changed, external filters, fuel water sep. and Yamaha mech has checked VST for issues, he cleaned it and re installed. Ran fine for first two days and problem has re-occurred. Kicker is, If I turn engine off and leave off for approx. 5-10 min. and restart, 9 time out of 10 it will run fine at high rpms (2500 - 5000) if I bring it back to idle spd, within 10 min. it will stall. Checked gas tanks and one has some debris in it (particles) This has been ongoing for last 2 weeks. Can still use it because it doesn't get worse, same scenario every time. Help please?