Your engine sounds okay to me...try using a couple of temp guns off your friends or something and compare the differences. I noticed my old engine goes a little lean when the tank has like -20% left

On the cautious side, its always a good idea to seal your engine. Removes a couple of future problems your engine is going to have. You have to use Sensor-safe RTV silicone sealant like Permatex and you seal the backplate, carb neck. Those parts use o-rings that can leak and deteriorate overtime.

You can also further seal the shims/gaskets for the tuning needles and the lock thing that tighens the carb to the crankcase, forgot what its called..