Engine tone beating under acceleration

[Doddsy]

I took my car out yesterday for a long drive and Im pleased to report that she is going very well. Pulls all through the rev range (went to 5.5k) and didnt miss anywhere. One thing that I am aware of is that the engine tone has a low frequency “beat” to it (circa 1/2 second). It is only apparent when the throttle is quite open (half to full).

Does anyone have an idea of what could cause this? I presume it isn’t supposed to be there. This isn’t new either and has been there for a while (years).

I have tried to ensure that the accelerator linkage is matched to each bank following the manual (but this isn’t easy to do). Advice here would be appreciated too. I will need to recheck this but is there something else that could cause this sound?

[jagwit]

Check the engine mountings. Particularly the one on the RHS. This caused the rhs air filter housing to be touching the body frame.