I bought a 01 chevy duramax with 60,000 miles two months ago. This weekend, we took a trip. Truck had been running fine and didn't have any problems before. My friend gave me a juice edge power chip to use and I loved the power and had no problem while running it for a month. So about the knock. We were about 100 miles into the trip doing 70 mph about 2,000 rpms when all of a sudden it sounded like the engine was getting noisier. About a mile later, it started to knock real loud and thought that the engine might blow. Slowed down to 50 mph and was still there and so I smashed it and took it to 90 mph and didn't knock in acceleration and the performance seemed to be there. But as soon as I left off the throttle, the knock was there, It was only knocking if you were holding the throttle steady and there was no knock when you were off the gas. Pulled to side of road immediately, and got out and opened the hood (like this was going to do any good) everything looked fine and truck sounded ok and I got back in and started driving and everything was fine. Took it right back to 70 mph. It seemed to be a tad bit louder but maybe I was a bit paranoid. Drove 200 more miles and it happened again. It sounds like it was injectors or maybe timing. So I decided to pull the chip and drove the 800 more miles at 70 mph and had no problems and came back 1100 more miles and no problems. Have not put the chip back in, don't know if I will or not. I was wondering if anyone had experience this. Is it a truck problem or a juice edge problem or are my injectors going bad? Injectors were never changed. I don't know if I should take this to the dealer or not because he may not find anything. Appreciate any help.