GMC Repair: 1997 GMC Yukon 4WD 8L; 233,000 miles, gmc yukon, first tank

Question
My Yukon has a knock in the engine that doesn't occur after a cold start.  It only occurs after the vehicle has warmed up.  It is especially loud when going up a hill or accelerating.  I have changed all the spark plugs.  I have also noticed a surge when I hit about 30 mph  It seems that the vehicle accelerates without depressing the pedal.  I tried buying better gas and putting additives in the tank.  This seemed to help the first tank we used.  However, it has not helped since.  The "Service Engine Soon" light is on and the code is reading as "Cylinder 5 misfire."  Can you help?

Answer
Hi
Is it a knock or a ping?
If it is a knock, you'll need to get the #5 cylinder checked.
Check compression on this cylinder. Preform a "running" compression check. Check the injector.
The clue to your problem is the Code for the #5 misfire.
I Hope this helps.
Good Luck
Pawl