I have recently picked up 454 suburban with an odd timing/fueling issue. The guy I bought it front said it had an intermittent miss but not every time he drove it. I haven’t drive around much other than off the trailer but I seemed to run just fine then, but I started it the other day and if I rev it up in just park it wanted to stumble over and live cut out. After idling for maybe 5 minutes the idle raised probably 500 rpm for a few seconds then dropped back down. I know before I bought it he had replaced, dizzy (whole distributor, cap, rotor, icm), plugs, wires, Egr, tbi sensors, fuel filter, both coolant sensors, and who knows what else. I haven’t checked the o2 sensor yet but I will probably change it in the next coming days along with rebuilding the tbi and upping the fuel pressure spring. Any help would be greatly appreciated, just wanting to get the big momma on the road for some cruising, thanks!