ok so i had a blown head gasket so i pulled it down and replaced them. This is on a 99 ranger 3.0. now ive got it all back together and it runs but runs rough. when i give it gas in park it backfires and blows the DPFE hose off and then when i rev it with the hose off it blows a little fire out of the tube. It will rev up in park or neutral but when i put it in gear it stumbles real bad under a load. When i try to rev it in gear it just acts like it wont take the gas. i can hold it to the floor and it will only rev to like 1500rpm's (just guessing on that #) I had my friend hook his snap-on scanner up to it and it wont detect anything, he looked at the oxygen sensors and the MAF
sensor to make sure they were doing what they were supposed to. I pulled all the plugs out (They were brand new-only about 20 min idleing run on them) was cylinders 1,2,3 (passenger side front to back) were still almost brand new looking porcelin was still white. Cyl 4 (driver side front) was BLACK and cylinder 5 (Driver side middle), and cylinder 6 (driver side rear) looked like my old plugs that i pulled out that had about 50,000 miles on them. I have checked and rechecked all my vaccuum lines and ground straps and they are all correct.. Any ideas?