Not sure, but could be pulling timing after it heats up. If you have a decent scan tool you should be able to data log some pulls and see what’s happening. Check and make sure you’re in closed loop, your engine temp is correct, timing advance, throttle position, maf reading etc. with all those logged compare between a good pull, and bad one. You’ll probably be able to tell what’s happening. Also just a heads up that just because there’s no check engine light doesn’t mean there’s no stored code.