 Stalling
What Veronica said , is where I would start.
Secondly , does the replacement Carb. have a dash-pot?
Is the Dash-Pot adjusted properly?
The design/reason behind the dash pot ( I believe ) , is to allow the
engine to recover from an open-throttle to closed to idle ,
MORE SLOWLY , so as to recouperate from the Loss & Sudden GAIN
in Manifold vacuum , making at times, the Carb LOOSE it's vacuum,
and thus, USUALLY , either FLOODING OUT , or in some cases lack
of application of vacuum to the base of the Carbureator -
ie. loss of bottom vacuum = loss of fuel delivery.
ALL in ALL , I would first start with what VERONIC said, then , start
looking for a correctly adjusted dash-pot ( aka: De-cellerator ).
How is the vacuum on the engine = consistant , or is there possibly a
vacuum leak at the BASE of the carb or manifold? Well , let's not jump
ahead , first start with the STRONG SMELL OF GAS you indicated,
by trying the VERONICA remedy.
Enjoy your CLASIC ride!
Joe Z. | 
let me start by saying I am far from a gear head so don't get to tecky with me. Here is my problem, I had the engine rebuilt added a mild increace in the cam but for the most part its stock, installed a edelbrock performer 600cfm carb and matching manifold. The mustang is a gta (automatic) drives great idle is good but if I hit the gas hard and let off to quick it stalls every time ( but only when it is in gear) also it has a strong exahust smell. any ideas would greatly appreciated. thanks
: I think that the first thing that I would try would be turning those two idle screws in about 1/4 of a turn. If that helps, dial it in with 1/8 turn increments until it's right. If that makes it worse, back it off to where it was plus another 1/4 turn and see if that helps.
