99 Cherokee Stalling

I've had great luck with this jeep until this month. It is only used on the weekends, maybe 50-100 miles a week. First, it started
to sputter a bit when it was warmed up and put in reverse only, but always came out of it and ran well. Then last week, after
sitting in the garage all week as it usually does, I get in it and try to start it, but all it does is turn over and nothing else,
like it is not getting gas. After trying for half an hour, I have it towed to the dealer. Next day they call and say it started
right up. They hooked it up to computers, say everything is fine. They check everything and recommend plugs, fuel filter, and clean
injectors. Worked good last weekend, started right up this morning, go to the grocery store, come out, starts right up, put it in
reverse, it dies. Try to start it 5 more times, and it just sputters. Let it sit a few minutes. It fires right up, and has been fine
all day. Kinda hard to trust it. Any ideas?