1996 GMC Truck Yukon engine missing at idle

I have a 1996 GMC Yukon with the 5.7 liter engine. The motor misses at an idle. The code says it is missing on the number 5 cylinder. I have done a compression check and found 140 psi on the #5 cylinder and a 150 psi on the #7. I have changed all the plugs and wires, in which the issue has continued although better for a short time. The plug fouls with a crusty white color. The engine also is idling fast at 1500 rpm with an error that the engine is idling faster than expected. If I pull the spark plug wire off of the number 5 plug, the engine does not change the rough idle at all. There does appear to be spark if I connect an old plug. Please point me in the correct direction. Thanks!