Yeah, might be an air leak at the carby, very common problem but hard to detect as it usually happens at running temps. What happens is the alloy and plastic parts of the carb expand at different rates when heated, so it leaks where the plastic(composite, whatever)and alloy pieces join together. If it runs fine, then when it gets into the 200+ range starts acting up like the idle seems to hang up when you let off and temps start climbing fast, then this is prolly the issue. Either send it back for replacement/repair, or seal it yourself where the different materials join. A couple options that seem to work are a couple thin beads of red locktite ONLY where alloy meets plastic(obviously remove carb first). Put on a thin bead, let it sit overnight, repeat. Or JBweld in the same areas. I used ultra copper rtv sealant on mine, but after a couple gallons it seems to have started leaking again, so I'm gonna try the locktite first, and if that don't do it, the jb weld. Just be sure not to locktite or weld the carb into the case. Let us know how it goes.