86 Cherokee Acceleration @ low RPM

Hi all I am having problems getting my 1986 Cherokee
Pioneer with 2.46L engine and Throttle Body Injection, to give a smooth
acceleration under load. Seems to be more pronounced during the lower part
of the power curve. Downhill it seems to have great acceleration. (No
Jokes Please) When it starts up a hill it slows down and depressing the
accelerator pedal seems to make it bog down worse. Depressing the pedal to
the floor seems to really cause it to bog down. If I downshift to a lower
gear and get the RPMs up it seems to be better. But with many hills I have
to go down two or more gears to even get it over the hill. The hills are
not all that great. Have tried changing the Map Sensor, checking the hose
connections around the TBI for vacuum leaks, all hoses for good connections
and proper placement. When I remove the injector from the Throttle Body I
found only one small O Ring at the bottom. (My manual shows two. One near
the top of the body) I tried replacing it but still have same results. Any
suggestions of something I might check and/or have missed? Is there any
computer codes used on this model that might give me some clues as to the
problem? One again thanks for all of your help. Don Smith