I have some MT62s, the one I'm playing with now is in a SD260 30% extra.

My problem is it's dieing on rapid throttle advance from idle. I've got the ignition set at 28* BTC static, and have replaced the soft carb block with one from Ralph made from G10. I'm getting 7400 rpm with a Vess22A and 7200 rpm with a BME 20x10, the same as my Brillelli 366GT. The plug looks good, very light brown. The idle is set at 1850, it will idle down to 1350, but it's a little rough there and 1850 works fine while flying. I've gone leaner on the low until it's really hard to start and dies lean on any advance of the throttle, and I've gone richer until it's slobbering. I'm running a KS86 canister with a DA header from TBM, it has no effect on the top-end compared to the stock muffler exactly the same power readings, just halve the noise. When I took the cowl off to tune the transition, the engine was wet with fuel/oil. When I ran it without the cowl I had to re-tune the end for top-end, then I noticed if I blocked the prop-wash from the engine I had to re-tune it. I fly with a cowl, dah, so to tune it without the cowl I strapped on a plate that blocks the prop-wash, as if it was in the cowl. Now I see where the gas/oil mix all over the engine came from, when I pop the throttle open a air/fuel mix fog comes out of the carb, it's not blown away like it was before the blocking plate. So tonight I'm going to turn a velocity stack about 1 1/2" tall and see if that helps the transition when I pop the throttle open. Anyone got any other ideas.