Hello all, I hope everyone is well....

I am having some issues with my 1995 E320. A few weeks ago I replaced the air filter, plugs, and the connections from the coil packs. I noticed that I have three different coil packs, and I believe I put Bosch Platinum plugs in, which I understand the M104s do not like. Right after I did those things, the car would have an occasional misfire. I checked the connections, and one was a bit questionable, so I re-connected and it got better. This morning when my wife went to drive it, it started like very rough. She turned it off, then back on after calling me, and it was better, but not great. It seemed to smooth out after it got warm. The car was parked with its nose down hill( I know this sometimes comes up with the diesels). When I got home I went out to look at it, turned it on, all seemed fine,and gave it some throttle. at about 4000 RPMs(a little under), it acts like a rev limiter is kicking in. It stumbles pretty bad. My CE has been on for a bit with codes 6 and 12. Also the wiring harness has been done. I am stumped, is this a throttle issue, an ignition issue, and fuel issue? Due to the skip, I am thinking coil packs, but the stumbling at 4k has me perplexed(mass air?). PLEASE point me in a direction! The car only has 140k on the clock.