MDP1

My 2015 yukon xl denali with 195k miles, has had a check engine light on for 6 months. Periodically, it begins flashing, begins to run really rough. Then, it stops and runs smoothly. I have taken it to multiple places, including the dealer without someone finding the problem. I have replaced many things...,full tune up, CAT, O2 senors, MAF, high pressure pump, transmission coolant lines, air ride compressor, new struts, front shocks and coil springs, etc. I suggested replacing the ECM....they all think I'm crazy when I suggest this could be the problem. Am I wrong/crazy or have I drove the last miles on this vehicle?