2000 Ford 6.8 v-10 motorhome shakes and looses power above 50mps, can't go above 60mph. Looses power on hills?

Have a 2000 motorhome that has a Ford 6.8 V10 engine. On my way back from New Orleans we started losing power. I can get up to 50 miles per hour and it starts to shake I can get it up to 60 and that's as fast as i can get then it just slips and shakes real bad. The only way I can increase speed above 60 is going downhill and tapping the gas pedal increase speed otherwise going uphill I start to lose speed and can't accelerate without slipping and a lot of vibration. With the scan tool it said I had misfires on cylinder 2, 7 + 8. All spark plugs were changed and cylinder coils. Cylinder 2 still shows misfire and the problem has not changed at first I thought it was a transmission but now I'm not so sure

Are you going to keep guessing and changing parts, or just take it to a mechanic?

http://www.cartalk.com/mechanics-files

Have you checked the gas pressure in the gas line? It could be running out of gas.

Perhaps the gas filter is partially clogged?

Feeding 10 cylinders will take good gas pressure, and lots of it too.

This fellas might help.other yt'ers in the stack who might offer a solution,

problem was a worn through rubber boot affixing the pcv valve to the crankcase

Check for spark in #2 with a tester. Check if the the #2 cylinder injector is firing or getting command to fire with a noid light. You can try swapping the injector from another cylinder that is not misfiring and put in #2. If the misfire goes to the other cylinder, replace the injector. Check compression on #2.