I have a 93 with a 351 and e4od with 192k on it. Yesterday I added sea foam engine treatment to the crankcase and a small amount to a1/4 tank of gas. I then added sea foam spray to the intake via the throttle body per there instructions, which included driving aggressively afterward. After all this I changed the oil and filter and parked it for the night. This morning I leave for work and is hesitating and sputtering, but only when in gear, it idles fine,starts fine and doesn't sputter if you give it gas while in park or neutral. I thought the gas treatment might need to be diluted more so I filled up with 93 octane, normal gas grade selection for me. Everything looks in place under the hood, vacuum lines, plug wires, but driving down the road it will feel like it is plowing power, pops which I guess is detonation and hesitates like it has a misfire. I'm stumped.