07 rancher help

My rancher will start and idle but if you give it gas it dies. When you restart it sometimes backfires. IF you sloooowly give it has you can get it going. As long as you keep the RPMs up it will go. As soon as you let off it’ll die. I’ve changed the spark plug and the fuel pump ass.
Took out the injector and it seems clean. About to drive me batty. Anybody know what I need to try next?