Volvo Repair: 1988 VOLVO 760 TURBO WAGON, volvo 760, tank fuel

Question
THE CAR STARTS OK. WHEN DRIVING I LOSE POWER. IF I PRESS ON THE GAS PADEL HARD I LOSE POWER AND HAVE TO TURN IT OFF AND RESTART. IF I PRESS SLOWLY IT WILL RUN OK MAYBE 65 MPH BUT WHEN I COME TO A HILL IT SLOWS  DOWN AND ALL MOST STOPS OR WILL STOP. WHEN I DRIVE IT I PRESS ON THE PADEL SLOWLY THAN LET UP AND PRESS SLOWLY AGAIN RIGHT ABOUT WHEN IT SHIFTS.
I have had this problem for many years. The local dealer could not tell me what was wrong.  

Answer
Make sure in-tank fuel pump is working properly, if problem goes away on full tank, this is usually sign that in-tank pump is bad.
Check exhaust system to make sure there are no restrictions. I have seen the cat converter cause restriction and performance drop as you've described. May have to have off and check visually inside. Or if you have access to back pressure guage, this will be more accurate.