Misfires. Did Plugs, M.A.S., CATS ML320

[sdanville]

I am at wits end. I have been searching the forums for answers for weeks.
I have multi misfires. When I come to a stop I have only a few seconds before my truck shakes, the engine light blinks, and i have barely enough power to not get run over. I can pull over and restart and if I stay in motion the V6 runs okay. I can accelerate hard at times and go 90MPH+ at times when she hits on all 6.
History..
I now have 121,000 miles.
Problem started at about 118,000. It started accelerating slugishly. So I gave it more pedal to test and had misfires. I drove it like this for weeks feathering the gas and all was ok. Then it got worse. I bought a new Mass Flow Air sensor. Better but not right. I had only 3,000 miles on my Bosch platinum plugs but replaced them anyways. seemed a little better not sure. I had a cat converter recall and thought maybe plugged cats. Took it to the dealer and told them of the mis fires, but wanted to only have the cats replaced to eliminate them. The Mercedes tech said it was a bent vacuum line and said $80. I shrugged and paid happy thats all it was. It ran great until my 1st red light then stumbled again ( 30 miles from dealer is XWay) . I replaced the 3 week old mass air flow sensor with a bosch sensor today because I was afraid the last one was a cheap aftermarket and didnt work. Still wont idle.
I tested the resistance on one bank of ignition wires all seem fine. The codes show practically every CYL missing. So I cant imagine its plugs,wires,or coils.
The air filter looks fine, I replaced the fuel filter and pump at 100,000.
I bought a Code reader too last month. I get all these codes...PO300,PO301,PO302,PO303,304,306,306. previously I had PO170 and 173.
I have checked for vacuum problems..I dont want to buy a new Brain but am almost to that point.
Desperate in Michigan for accurate advice.
Steve