1993 Volvo 850 gas?

Engine Performance problem
1993 Volvo 850 Two Wheel Drive Automatic 118000 miles

I have a 5cyl 93 volvo 850 on accelaration it hesitates but as soon as you let off gas pedal and slightly push it down it will gain speed. There are no codes that show up using under hood factory code reader. (1-1-1)I have replaced fuel filter, replaced fuel injecters, the exhaust is not plugged. Fuel pressure is at 45psi?The distributer cap is fine as is the rotor. It will cruise a long time at highway speed but as soon as you push down on gas pedal it will hesitate until backing off and feather light acceleration will get it up to speed. It does this at any speed.A mechanic friend has checked out mentioned stuff above. It idols fine but also hesitates on acceleration. Any ideas on what do to next short of going to volvo dealer and opening my wallet? Thanks rick