Engine lags and stalls when initially pressing gas-Solution Found?!

IDK if that clip for the bowl vent does anything of running value 'cept hold the vent cap open a hair at idle. And a lack of that would not prevent the bowl from venting as the slot for the pump is not sealed. If it were a holley that had a vent that was actually sealed (opens with the throttle linkage) it may have an effect but I cant figure out why (from afar) that lack of a clip would alter anything. As for the seal lip folding over, take a look at the bore and maybe there is a ridge in there. possible a brake cylinder hone could smooth it out if a piece of sandpaper doesnt.