Won't initially hold an idle & alternator or something still whining a little

Can any of you help or know about this I recently replaced alternator in my 02 gt ( with help from the 3g club THANK YOU VERY MUCH!) When I start the car first time of the day I have to keep my foot on the gas for a minute or so otherwise it will die .It starts out idling kinda low , like 600 or so then about 800 ( which I believe is normal ) after it's warmed up . Also tightened the alternator belt and still heat a little whining sound .I cleaned the egr valve cuz it' was throwing a code indicating so . I did manually actuate it by sucking on the hose a little ( after it was cleaned of course !) then tried to blow through it and noticed the diaphragm wasn't fully sealing could that be the culprit . Would like some guidance frome anybody that knows or feels qualified to reply when ya get a minute thanks .