missfiring #3and#6 cylinders 2000 3.0 ranger

[jeep2001]

Check engine light came on a few days ago ,rough idle that seems to get better above 1400 rpms. At 50mph and above in overdrive truck shakes also. My friend scanner tool said missfire on # 3 and 6 cylinder so we replaced the coil pack but it made no difference. The wires and plugs are good, is there any way it could be the injecters? Is there a way to test the injectors and how hard is it to change them? Any help would be appricated.

Thanks
Mike

 

[Super_Swamper_98]

i know you said the plugs were good did you pull #3 #6 and check em?

 

[jeep2001]

I reset the check engine light 3 times afterthe first time and only got missfire on #6 cylinder. Replaced spark plup and wire on # 6 and the check engine light still came on and is running rough. I put some injector cleaner in the gas but it did not help,could it be a bad valve? I like this truck but is 140.000 miles too much for the 3.0? Any help would be appreciated.