misses at running temperature

88 ranger 2.9 the engine doesnt have as much power as it should.. when you drive it about half hour it will backfire through motor not a bad backfire though, mostly when you run through the gears quickly .. can tell motor has a miss to it, because it has a shake to it when running..

for more information, new spark plugs, wires, ignition module on distributor, new distributor cap and rotor.. could it be the injectors?

and it has poor throttle repsonse and when it gets over 3000 rpms it wants to idle back down when your still giving it alot of throttle