Running rough and will not pull up a hill in 3rd gear stalling

While driving a few days ago the truck started running rough and stalled a time or two and it would hardley make a very small grade hill in front of my house it read a few pages and found to check the coil packs and I found that it only fireing on 2 cylindders # 1&4 and 2 & 3 did nit have any spark from the wires I switched the cooi;s pack front to back and back to from nothing changed I had the imc checked at advance they said it was good since it had such high mileage I replaced the crankshaft sensor and still I have the same problem. Could the pcm or imc be bad and if so how can I check to find out which one is bad.L. Also thereis NO check engine light on.