I have an H16XL with a HH160 Tech. I have had the carb off and cleaned it, soaked it, blew it out, numerous times. Today I went through it again and put a kit in. Fired it up and let it run and warm up good running a good fast idle. At a third throttle and above it runs nice and smooth, very responsive. When I try to idle it down to just a fast idle it starts to run rough and shake a lot. It starts right off with choke and leave the throttle were it is, real fast idle. I have a HH140 in a G12 (re-motored) and it runs smooth at all speeds. I am thinking I might need a new carb. It has a Walbro LMH on it. I tried a carb off another HH160 with a bad ignition coil and that was no different, so not sure the carb is the real problem. I have run 2 tanks of gas through it with a heavy dose of Sea Foam. At slowest speed to keep it running it will miss and little puff of white smoke will come out the muffler. The misses are about 10 to 15 seconds apart. Any ideas would be greatly appreciated. I am not much into the Tech engines. More the Briggs and Wisconsin's.