Uhh if you're blowing into the cart to get the game to run because of random freezes, you're the cause of those freezes. Blowing causes hot moisture to leave that swamp rot you got going behind your gums to fly onto the connections. This swampy invisible spit causes the connections to temporarily work better due to conductivity, but over time it causes the blackness to collect, and if you're lucky more green and white crust much like blow out battery compartment rot and you're screwed.
Blowing in a NES cart is the WORST thing you can do short of being totally stupid and soaking it in a sink and dropping it right in drippy wet.
Just get some isopropyl alcohol and a q-tip for the cart, or better yet use that on a NES cleaning kit wand + on the deck cleaner too and give it 30sec to dry. I know it works, I got a 1985 unit with the original pins and it fires up like new nearly every time still. If I do fight with it, it's a dirty cart.