I just put a new (junkyard) engine in my 92 SL2. At idle and above 1/2 throttle it runs like it should. But at about 1/3 to 1/2 throttle the car just doesn't want to go, kind of chuggs or hesitates. Any ideas would be greatly appreciated. Not worth shelling out wads of cash to the dealer to diagnose. It has new plugs, and i checked the tps and it is o.k. Thank you