D15B7 engine "lope"/"sputter" when accel

Yeah so when starting out in lower rpm through every gear I'll accelerate and the motor is sputtering and gutless until about 3500-4000 rpm. The idling Rpms are low to... Getting all the way down to 350-500 rpm. Dunno if it's timing or what. Just seeing if you guys have a couple of thoughts to throw my way. Thanks.