I purchased a 2003 crewcab 3 weeks to good. It seems to drive great 95 percent of the time. I wanted to know what to look for if there are injector issues. I have checked the oil and it dosen't smell at all. It does seem to have a weird consistancy. There is no smoke, oil presure seems to be fine. I also have noticed a vibration that has come and goes at highway speeds. It has happened twice and both time the vibration went away in a couple of miles. Felt like a tire was out of balance. Any ideas?