my '97 ram 360 has a #6 misfire even after a tune up and replacing the spark plug twice. It lugs mostly at low rpm's in forth gear, runs smoother at high rpm but kinda low on power with some random backfire.first spark plug was sooty with a white tip. any thoughts??

 

Do a compression or cylinder leakdown test.

 

i did a compression test and it held 115pounds. i checked spark its good.

 

Do you get good spark at the spark plug end of that wire? If so, swap the injectors on 6 and 8, see if the miss migrates.