Danslssr

I have a 2006 Impala SS. 5.3 L . When i've been driving down the interstate for 20 miles or so & go up an incline the engine goes to 8 cyl mode a big puff of blue smoke comes out the exhaust. I have a misfire on the plugs 1-4-6-7. The spark plugs have alot of carbon & oil fouled. When i first notice the miss if I drive the car in 3rd gear instead of Drive it won't go into 4 cyl mode & will clean it's self out for awhile.I would like to disable the displacement on demand feature but I can't figure out how to. I tried unplugging the connector under the intake but that makes the engine run real bad. Is there away to disable the displacement on demand that doesn't cost too much ? Thanks Dan