here it is
normal is 17- 22
normal for the stock cam is 18-21
if you advance the timing, you get more vaccum. mine stays around 20.
you should check for an intake leak or leak in the vacuum tubing to the gauge. auto meter gauges never read right, but if its that far off, i dont think its the gauges fault. my gauge read 14 psi when i was running 17 and it read 20 inches during a heavy deceleration when it should read 25. enjoy.
1990 Stang GT
402 (4.00x4.00) engine w/ 8.5:1 compression, W351 svo block, arias custom forged pistons, 4340 eagle crank and h-beam rods
Ported TFS TW heads, dual springs, forged 1.6 rr's, link bar hydrolic rollers, billit custom (bigish) crane cam
80mm C&L MF, 95mm Holley TB, cobra intake
1 5/8'' jba headers, 2.5" strait pipes to flow bastards w/ turn downs
tremec 3550, 3.73 rear end, steeda shifter
kirban AFPR, Lucas 38 lb injectors, 255 holly intank, bosch high flow pump
accel billit distributor, crane wires, PS-92 coil, HI-6R ignition
PMS, mark VIII fan
Drag bags, 275/60-15 BFG DR's
and oh ya . . . a ProCharger.
as they say, "heaven is being stroked and blown."