MARAUDER BACKFIRE HELP
 

I bought a 98 Marauder with the cobra slash cut exhaust. The battery was bad and it had the wrong battery. I replaced it with correct specified battery. I installed it with the terminals reversed by mistake since the old battery was reversed and it was dark when I did it. It blew the 30amp main fuse, replaced it, but after that it backfires under the slightest acceleration. Replaced spark plugs, they showed signs of a rich mixture. What else could I have damaged? I am waiting for a repair manual I bought, but I doubt that the manual diagnosis stupidity like the wrong polarity when installing a battery. Any help?