The biggest plothole, in my opinion was the symbiote attaching to Peter's suit. Where the hell did his cowl/head mask part come from? The symbiote just attached to his suit and then it covered his head, but the suit stopped right at the neck. I know it's there right in the next scene, but I never really bothered to question it until now. Is the symbiote so sophisticated that it create its own exact replica of a head mask that Peter wasn't even wearing then?
All other plotholes, to me, were not significant enough for me to remember or care about right now..
-TNC
I wondered that too, in the end i just assumed that the suit created the mask through a combination of the knowledge of the basics of the suit he was wearing on the rest of his body and Peter's knowledge of what the mask is supposed to look like.