2004 sportsman 700 efi nightmare help!

New to forum. Thanks. Great site. I bought a 700efi off a guy. He said all it needed was the tbap harness. Seemed to run ok. But had codes an an ocassional back fire. Take it home replace the tbap wiring. No codes now run ok. Take it for a ride. Steep uphill. Says it’s hot. Let it cool baby it home with no hot light. I wash out radiator. Seems to run ok. Then all of sudden going downhill once in awhile losses all power. Pod shutts off machine dies. Started it back up runs ok but now the fuel gauge bars on pod disappeared. Any ideas? Also left front tire bottoms out into fender once in awhile on hard bumps. 26" tires.