Buddys 90 with the six banger has the same problem here in Vegas all summer. He put some heat shield in between the tank and the skid. Got a new heat shield up on the intake area. Wrapped the fuel lines with something shiny and is going to wrap the headers. So far it stopped the vapor lock just has a little trouble starting hot. So full throttle and it goes good on star up. He is running a 95 MPFI setup on his.
I don't have the answer on the wiring being different.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184