2000 7.4 liter 454, L29 based engine. I recently did a compression test, both dry and wet, and all cylinders were about 135-145 except cylinder #1 which reads 160 psi. I have my records from doing a compression test on the same motor about 10 years ago, and the same cylinder had the same high reading. Its actually a boat engine- the first reading was at about 200 hours runtime, the current compression test was at 600 hours. Comparing to a car, think 1 hour runtime is about 100 miles, so first reading at 20k miles, current test at 60k miles. Engine runs fine. No knocks, no oil burning, makes full power. 2 different compression test tools were used. I cannot explain 1 cylinder having abnormal high pressure on a compression test but otherwise running fine. Help me understand how this can occur ?