2004 Mazda 6 s P2101, P2110, P2100 just bought car, don't Know much about Mazdas. It was overheating thermostat was stuck I replaced thermostat n a hose. Now it's not overheating but won't go over 2000 rpm n hucking n bucking, also with no help from me it revs up n down on its own also hard shifting. I am capable of DIY projects but don't even know where to start. Please help I love the way car looks but would love to drive it ,also.