Hi Chris,
I'm definately no expert but here's some thoughts... Have you looked at the
oil pressure sender and filter area as well as dipstick receptacle, from memory they are all on that side fwd section of the engine which I guess would align with your footbox. Have you removed the PCV and ran it that way? Just thinking excess crankcase pressure or blocked inlet manifold port.
Can you get access to a dyno and run it under load that way so you can then look around whilst stationary?