have a vac gauge hooked up to carb...was working properly...now climbs to about 15 and reads steady no matter wheater stomp to floor or running back pressure down hill...when shut off take about a minute to drop to zero.....do I need to replace gauge?????

There's something restricting the feed to your vacuum gauge; most likely, the line is kinked or, more likely, partially melted. In cold climes, I've seen ice block a line too. Many gauges have a restriction that fits into the line or is mounted inside the nipple to slow the response down and prevent excessive wear on the internals - it could get blocked too.

I am willing to bet it is partly melted,I did move it away from exhaust...and it was reading correctly the other day 20 at idle and maved with go pedal/decel...thanks

hose changed out ...working fine again...thanks