Just got my car back from getting my transmission rebuilt and now i have been hearing like a ticking sound or pinging sound (almost like something is flapping but it is very faint) that gradually increases as i accelerate i heard that it could be the change in gas because i used to use regular and about a month ago i started using the middle grade. Could that be it or is it something else? also i am looking to take my car back in next week and get a full tune up i have only had the car for about a year and i dont think the previous owner ever really got a tune up how much do they cost?