Any help is appreciated! Trying to diagnose what the heck is wrong! Refrence: My Dad owns a ‘98 2500 with the 7.4/454. We just did a tune-up (new cap, rotor, plugs, wires, spark plugs, and fuel pump) after replacing the ignition switch since it went out. Afterwords, the pickup is hard starting but idles and goes down the road great. Here’s the big issue: when you add more throttle and try to get a downshift, there’s a very hard misfire likely in multiple cylinders. What in the world could be wrong?