From what you say it sure sounds like the idle mixture is too rich or the choke is staying (partially) closed. Hopefully it's not flooding.
Symptoms of this are easy cold starts, hard hot starts, once warm idles so low it stalls, poor throttle response, and having to keep the idle up with the pedal.
First check to make sure the choke FULLY opens once warm, find this out by simply firing it up when cold like you nromally wouldbut with the airbox removed. Once it's running walk around to the front of the car and inspect the carb, the choke should be closed when it first starts then should move to fully open once warm. If it seems to be taking more than 3-5 minutes to move rev it up & down some and check again. If it's still partially closed your electric choke is failing - switch to a manual unit, these are far more reliable and better for performance, fuel economy, hot/cold starts, etc - there's absolutely no con to them besides you'll now have a choke knob under your dashboard.
If the choke opens up fully then it is fine and what you have to do is adjust the idle mixture & idle speed. On the BACK of the carb in the CENTER of the "base" is a cylindrical casting pertruding about 3/8" out of the carb, inside is a flat-head screw - this is your idle mixture adjustment screw. If you carb has never been properly rebuilt then this screw will be hidden by a welsh plug you have to drill out before you can adjust your idle mix.
If this is the case the carb must be removed to drill it out (drill a small hole into the plug and use a thick wood screw to pry it out, don't go too deep or you'll damage the mix screw inside) and since you're holding the carb in your hand remove the idle mix screw and polish the tip. Put the screw back in as many turns out (from bottom) as it was before, turning it out (counterclockwise) makes idle rich while turning it in (clockwise) makes idle lean so turn it in 1/4 of a turn. Now reinstall the carb and try it out, if it needs adjusting you can do so with a pocket screwdriver - find out which fits best while you hold the carb in your hand. If the carb is from a 1.9 the idle mix screw might be an allen head, it will be a very odd size (like 7/32" I think?).
Either way it will still need adjusting once the carb is back on, but fire it up first and get it warm. Once warm you can start adjusting, just remember righty-leany & lefty-richy. You know when you have it right when it idles really smooth and when you blip the throttle it has no hesitation. Also when you rev up and let off the pedal is should go straight to idle without hanging above idle or dipping below idle, it will also restart hot without any throttle.
While doing this you do have to adjust the idle speed too, it will be a large bolt hiding under the choke unit pointing backwards like the idle mix. Before you touch this loosen your high idle speed screw some, this is the one that goes into your choke unit. If you have to decrease idle speed this can hold it up so we must make sure it's turned out a little ways. Some times the idle speed screw is philips or straight-slot, but you can turn it by hand if your fingers fit - turn left for lower idle & turn right for higher idle. You want idle to be between 750-1000rpms once warm, it might also be happy above or below that but keep in mind when you use the brakes the idle can raise a tad or dip some which can make you stall at stops if it's too low or grind into reverse from a stop if it's too high. Once you have idle speed set check your idle mix adjustment again, if it was too rich then the idle screw was likely turned in a ways to compensate for it but regardless the idle mix will be set differently if you idle at 780rpm than if you idle at 940rpm.
If you're all done and happy with your settings button it up and go for a spin
After you park it you'll have to set the high idle speed when you next cold start it, you start it like you normally would cold and once you "set the choke" (hold the throttle at 1200-2200rpm until it holds itself up) you can remove the airbox and set the high idle speed to your liking. This is done by turning the screw that goes into the choke unit, turning it in raises your high idle while turning it out lowers it. Now PAY ATTENTION, there are 2 high idle speed notches so if the screw is only on the lower one make sure you're setting that high idle to only 1500-1700rpm because the one above it will be signifigantly higher. If the screw is resting on the top one set it to 2000-2400rpm (I like 2000-2200rpm), now if you set it on the top notch then the lower notch will be what it is - they're proprtionate to each other but they're inconsistent between vehicles so there's not set rules for them. Just know that it's easier to set the upper notch knowing the lower will be fine than it is to set the lower one not knowing how high of an idle the upper one will be.
Hopefully you can follow that all well, it's much easier than I might make it sound but this way you know the ins & outs of everything you're working with AND you know what you should be looking for vs what to expect with each adjustment.
