Note, some change in engine RPM's is to be expected with a load change. Examples include AC turing on or turning the steering wheel.
A low idle in response to a load change is usually a sign of poor cylinder balance (IE one or more cylinders not pulling their weight). Usually ignition related. The other key is the idle is fine otherwise.
could there be something wrong in the tune. I have longtubes and have yet to get it tuned correctly. BAMA keeps sending me a tune that really messes with the idle