Just rebuilt '96 LT1 in a C4. When I fired it up Sunday it took 2-3 ignition cycles to get the idle learn process going but it finally smoothed out. I drove around town gently for maybe 5 miles and then parked it. Didn't drive it at all on Monday. This morning (Tuesday) it cranks up OK, idles high for just a few seconds, then idles way too far down likes its a miss. The scan tool shows P0303. I cleared the DTC, checked all the cylinder 3 wiring and started it up again. Now it's P0307 (cylinder 7 misfire). So I clear that, then I put a timing light on all 8 spark plug wires. All 8 have good fire. While I was checking with the timing light it sets a P0300 random misfire. Could the misfires come from having the valve lash set too tight? What other explanations are there? And what changed from Sunday night to Tuesday morning? This is really a bummer since the rebuild otherwise went very smooth.