Wait a minute - we've spent alot of time linkin this problem to carburetion...... Now am thinkin: What about timing chain stretch of 10 degrees or worse that robs performance under load.

We can roughly guage timing chain stretch by setting the engine at TDC then comparing difference between TDC mark on the crank pulley with TDC mark on the forward camshaft stantion. They should line up exactly without even 1/8" difference.

How many miles on that 6 cyl Heckflosse 110 thats been souped up with Webers...... has the original timing chain racked up anywhere near 150k over the past 38 yrs?? Thats nothin for the short block, but valve gear and timing chain can need work each 120-150k miles or so.