Drill a hole in the firewall just below the engine compartment fuse-box. Use a grommet in the hole, feed the wire through and seal around the wire using silicone.
This is the right way to do things.
133whp-126ftlbsTQ Eclipse CD8443,Eclipse PA5422, JBL GTO751EZ, PPI 356cs(Rebranded A/D/S 346cs), JBL p1024, SubThump enclosure, RAAmat BXT, Damplifier Pro
Hatch Nation #140
Caeci caecos ducentes