Wet layup mold to infusion mold

Hey everyone im looking for some advice on converting some old hand layup molds to infusion. These were some of my first molds and ive added a flange to one and tried to infuse but there are some pinholes and airleaks that i was unable to shutdown. Ive laid more glass over the back. Really tried to lay it on thick and ive tried even gelcoating over it. Im wondering if its not a lateral leak in the mold and this is why im not able to close it down. I can see where air is entering when making a part but applying anything on the back of the area doesnt cure the problem.

A friend suggested to put some glass on the back and put the whole mold in a bag and infuse using mti hose.

Short of remaking the mold which is problematic if i cant make a leakproof part to infuse a new mold from is there any way to fix what i have? Im probably making it harder than it needs to be but ive tried a decent number of things to make this one mold infusion capable and so far im not having any joy.

And i still have a bunch more molds id like to upgrade.