Hey all new guy here. I've been having a problem with my 92 f150 I just bought. straight 6, 4x4, automatic tranny. When I shift into reverse it wants to stall and sometimes die on me. Only at the point of shift, once it's in reverse it's fine. Shifts fine in all other gears and drive great. I recently changed the plugs and wires, vacuum lines, pcv valve, egr valve, air filter just trying to diagnose the problem. What else should I check/change?????