engine ping then knock on 1995 Chevrolet 1500 Pickup

my tuck pings then turns to a small knock until you give it more gas i have put in a knock sensor it helped for around 20 miles

The pinging may be from a bad EGR valve. Any Check Engine or Service Engine Soon Light coming on? I assume that your timing is on the money and that your truck is not over heating. Check out this Article, the CEL is about a problem, not maintenance.
If the truck is heating up not over heating at highway speed is that a different problem? I have the ping as well