1994 Mazda b2300

Engine Performance problem
1994 Mazda b2300 4 cyl Two Wheel Drive Automatic 129000 miles

I have several problems going on but I think they are all related. 1) At stop lights/signs, truck runs rough/shakes. Sometimes I hold the gas pedal to increase the rpms, or I put it in neutral which helps a little. 2) If I leave the truck idling for a few minutes(in P or N), when I drive away there is a bunch of smoke. 3) My commute is only 5 miles everyday, but if I drive the truck longer where it can warm up, the engine pings/dings/knocks and smokes. It is worse when I put low octane gas. 4)I understand that the truck is a 4cyl, but it is slow to accel, sounds like it is bogged down. I thought these problems were attributable to the DPFE or EGR, but the truck seriously does not have one! I replaced the MAF sensor, which seemed to help a little. I also checked the airfilter and plugs/wires all fine. What else could it be? Thermostat, fuel pressure reg?
April 28, 2010.

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