Spark knock

I have a 98 4.ol / 5-speed sport with 65000 miles on it. It has been well cared for and tuned regularly. The problem is spark knock that seems to be getting worse lately. It has a new cap , button, plugs ( the proper oem ) ones, air filter, oil, etc. I did not mess up the firing order when changing the cap either. The engine runs great and smooth at idle but on a hill at light throttle it spark knocks bad. I have even switched gas companies and grades of gas and no help. I don't think it has an egr valve but if so could someone point that out to me and what about a knock sensor. Any ideas would be a great help. Thanks.

could be a little carbon build up on the pistons.you could try running some combustion chamber cleaner through it

I changed the plugs to NGK and the knock is gone.

interesting.thanx for the update