I have the same problem with my 09 GT in that when first started and placed in gear it sounds like a diesel for the first minute of driving then goes away. i thought it might be valves, but not sure.

I have an 09 GT that has a weird engine noise (diesel) when i first start the car. but the noise actually starts when i put the car in gear and drive off. soon after it goes away. another thing is that rattle noise not very loud but every time i hit a bump it's in the dash. i had heard that it was s...