Hey everyone, its been awhile since ive been on the forums and thats because my FSB is no longer mine. I traded my brother my truck for a 65 mustang. Anyways we dropped a rebuilt 351w with roller rocker from a 90 f-250 into the fsb and trying to get it on the road. Problem, truck starts up fine but struggles to hold idle. It will idle high for a bit then stumble and/or die. Also engine temperature seems to get up in the high side yet the upper radiator hose is still cool to the tough while the heater hoses and lower radiator hose is freaking hot which can mean to me either there are still air pockets in the system or the thermostat isnt opening. Ran KOER test 3 times and pulled code 18. Replaced SPOUT connector and still code 18 appeared. Going to swap out TFI modules next to see if thats the issue. Can't check timing since truck wont hold proper idle. Is there anything that im missing? Thanks for your help everyone and long live broncos... and mustangs.