Hi I'm new to the forums. I recently purchased a 2006 LR3 HSE with 120k that needed head gaskets. I bought a new engine on ebay with only 68k on it and swapped it a few weeks ago. I recently towed a few snowmobiles for an hour or two and then noticed my rpm's "hunting" up and down a hundred to two hundred rpms between speeds of 25 and about 60. I went to the local transmission shop and he thinks it's an engine misfire and not anything to do with the transmission/torque converter. I have no engine/DTC codes. The rpms fluctuate mostly at the lower RPMs say from 1800 to 1900 and so forth. They can be felt while the vehicle is slightly under a load and the RPMs are also visibly changing when the vehicle is going downhill without a load on the engine. What do you think I should do? Also, the RPM fluctuations are less noticeable when the engine is cold.. sometimes they're not even present (from what I can tell)

Any help would be appreciated.

Thanks,
Matt
18 year old, first time Land Rover owner