While in park or neutral my vehicle's rpm increases to an abnormal level about 3000 rpm or half throttle. when put in to drive or any other gear rpm returns to normal. while in drive vehicle will increase speed to about 30mph.codes that were pulled are tps and power steering switch. i replaced tps and checked for vacumn leaks. air filter clean pcv working. throttle cable fine t-plate seems to be moving fine. what could be the problem? Please help?