New to the LS1 game myself. Last year I bought a '02 Z28 with 41k on the clock. Piston slap out the ying yang (at least to the untrained ear....I was a Ford guy for 25 years), and what I think was/is lifter noise as well. Had a knock sensor code that took me a while to fix (had no time)......previous owner replaced the sensors, but got the wires pinched under the intake...thus an intermittent code. Fixed all that, SES off for good. Noticed a lot of oil in the intake, and was burning through a quart of oil every 2500 miles or so. While I had it apart, new plugs, wires, intake O-rings....and a new PCV valve. Oil consumption went WAY down. Can almost go a complete oil change cycle without adding any oil (always Mobil 1). Also noticed it had a 160 degree thermostat. After not being happy with the way the car ran in last winter's few weeks of ridiculous cold....put a stock Delco 189 back in it. 56k on it now, runs outstanding.....but still has occasional loud (to me) lifter noise. Is the low mileage plus years of running that colder thermostat aggravating my condition?