could it be this Improper idle mixture floats slowly plus or minus 1 ½ to 2 ½ inches or timing is off some -- when i watched the gauge it started at 15 and then went to around 14
found this
CONDITION INDICATION
readings are at idle unless otherwise stated. Gauge readings are in inches
1. Normal Steady at 15 to 21
........................
Drops to 2, then rises to 25 when throttle pedal is rapidly depressed then released.
2. Intake leak Low steady reading less than 10
3. Head gasket leak Gauge floats between 5 and 19
4. Improper idle mixture floats slowly plus or minus 1 ½ to 2 ½ inches
5. Small spark gap or defective points slight float plus or minus 1 to 1½ inches
6. Late ignition timing Approx 2 inches below normal idle
7. Late valve timing 4 to 8 inches below normal idle
8. Worn valve guides Oscillates plus or minus 2
9. Weak valve springs Violent oscillation (plus or minus 5 inches) as rpm increases. Often steady at idle.
10. Sticking valves Normally steady, will intermittently flick downward about 4 inches
11. Leaky valve Regular drop about 2 inches
12. Burned or warped valve Regular, evenly spaced down-scale flick approx 4 inches
13. Worn rings/ diluted oil Drops to 0, then rises to approx 18 when throttle is rapidly depressed then released
14. Restricted exhaust system Normal when first started. Drops