Wrecked 500 sometimes sputters when feathering at low speeds

Title says it all pretty much. I had a bad wreck a few months ago but the bike came out with very minimal cosmetic dmg surprisingly. It did sit outside in the weather for about 4 months while i recovered and it runs as if nothing happened but i like to blip my throttle at low speeds or at stops and sometimes it sputters for a second or two to the point it almost dies but then it will get back into normal running order...never does it at speed..never did it before the wreck....is it a ECU thing or dirty injectors...Its a toy and i beat the hell out of it and maintence only happens when it is absolutely needed (apart from Oil cahnges)