the mileage may be partly the carb [and choke], but the slow cold start is pretty common, have to pump a few shots in to start a small block that's been sitting for a while - with a manual choke, pulling it half out until it fires should help - do the pumping and choke just an instant before you turn the key - if the choke can be on without affecting a warm engine you have something wrong there, have you looked at the action of the butterfly when you activate the cable?
Bill
