Having some trouble with engine
So yesterday we took the Jeep to my family reunion, about 30 miles away. Ran fine the whole way, until we got off the interstate. It started running really rough, wanting to stall, and backfiring. We let it set for a few minutes, started it up, and it was fine. Then last night we went to a friends house. Took the interstate with no problems. Exited, and as soon as we started into town, same thing. Smelled strong gas odors, backfiring, and wanting to stall. Again, turned it off for a minute, started it back up, and it ran fine. I made an intake with an old K&N, and some p.v.c. Could the new air flow be affecting the computer? It only happens when we go from interstate speeds, down to city speeds. If I start off in town, and stay around here, it doesn't happen. Plus the fact that when I turn it off, and restart it, it works fine again. Almost like it's resetting itself. Ideas please. Thanks.