You could see if the throttle position sensor is unplugged/not working. I had a similar problem a couple days ago and discovered that my TPS was unplugged a couple days ago and it fixed my wacky tach gauge right up. As for sputtering, I'd check your spark plugs to see if they're firing properly... That's what I'd do, but I'm pretty new to dealing with these engines, so if someone sees something wrong about my advice, feel free to correct me.
