This Jeep has had new heads installed recently. Runs great. Check engine light comes on when decelerating. Can watch the misfires on the scan tool. Shows misfires on all cyl's, but cyl 1, 3, &5 seems to set at about a 2 to 1 rate over cyl's 2, 4, & 6. Have already changed plugs. Disconnected each injector while idling & found nothing wrong. Smoked sys for vacuum leak. Found small leak at throttle body shaft. Don't know if this is enough to cause a problem. Usually sets a p0300, but once set 300, 303, 304, 305. Has not done that again. This crazy thing is a 3.7. Surprise!