I just put in a brand new 242 amc I6 4.0 and sometimes when driving especially in lower gears it will chug/putter. It feels like its not getting enough gas or that the rpms are too low and it's about to stall. That's the easiest way to describe it. It's will "chug" 3 or 4 times, sometimes more and then be good for a little while. Any ideas?