GTR still stalling

I asked about this before and was told it was probably the AFM's. I sprayed them down with electron cleaner when I put new air filters on and the car ran perfect for about a week. Within the past week it has started stalling when I shift from 2nd to 3rd and 3rd to 4th. When I push in the clutch and give it some gas it won't rev above 4000 RPM's. I usually end up pulling over and turning the car off it's always fine on restart. I also noticed this happens when I'm driving slow or right after the car has been sitting for longer than a hour. I'll be paying the junkyard a visit to get the AFM's off a 300 but I'd like to know if there is anything else I should be checking? Any help will be greatly appreciated.