Is there any reason why this plug (yellow) would be left unplugged on a carburetor?
I took it to a shop and mechanic said that was causing a vacuum leak. So he plugged it (yellow)..
Right away I noticed my car wouldn't stall if I had to suddenly slam the breaks..
Also, the idle was slightly deeper between 700-800RPM, and choppy, which I loved! (Music to my ears)
But after a few days, I noticed that at red lights the idle would slowly diminish, to the point where it almost stalls out. So I...

Carburetor plug, throttle not as responsive