Who here has replaced a carb on a GS45 or G51? What carb did you use and does it solve the mid-range issues? In other words, can you now run it for 3-4 minutes at half throttle and then hit full throttle w/o a stumble or having it gradually load up? I've tried an ASP 40 size carb from Just Engines which they offer machined to fit the GS45. It works a little better than the ST carb - still stumbles a little. Anybody else? I'm wondering what has worked for people and what hasn't in terms of replacing the carb with no other modifications.