If it is at 2,900 rpm it could be the supercharger clutch engaging. This could be an indication that it needs replacing as you shouldn't feel a lurch either it should be smooth. The only time I have felt it engage is if I put it in 1st gear and accelerate very slowly and as you get to 2,900 rpm you feel a short "drag" on the engine as the supercharger engages. If you accelerate normally it is so smooth you feel nothing.