1999 Other GMC Models Stumbles on light acceleration

I have replaced the spark plugs, sp wires, dist cap and rotor, ignition coil and the V8 7.4L still stumbles under light acceleration sometimes bad enough to stall rarely but still does it sometimes.

recently the idle has been fairly errtic. Comperssion test is within in specs per manf.

any ideas I was thinking about finding out how to trioubleshoot the distributor itself.