well as i was leaving a freinds house in the blazer i got on it and pulled to 80-100 before i let out . thats when i noticed a misfire .i drove home limping . i then unplugged 1 coil at a time till i found the one with no change . i then pulled the plug and it was cover in black soot . i'am now thinking it might be a bad injector or a burnt valve . maybe yall can help . thanx in advance.