He everyone.

This is my first post. I did some searching on here trying to answer my question my self but couldn't find anything. I have a 98 Z71 with the 5.7L in it. It has right on 100,000 miles and I have noticed some knocking when going up hills or something. Also I don't know if its related but under real light acceleration I can hear the engine idle up and down not even 50 rpms even with a constant foot pressure. You can't feel it, and I didn't notice it till I got my exhaust put on. After 60 mph it doesn't do it as badly since the rpm's are up. Any ideas? I havn't put any higher octance gas in it because it shouldn't need it. I have had several trucks but none have knocked as badly as this one. I have ran some good injector cleaner through it several times with no change.