Hi can anyone help please? I have an audi A6 2.5 TDI, there is a leak from the sump, i need to remove and re-seal, is this very difficult? I have been told i have to remove the front subframe?

Also, my car has been chipped, i notice when i am driving it, when i rev over 3000rpm, there is a tappety noise coming from the engine, could this be the tappets or maybe the big end??

Thank you very mych

Tappets = sounds like its in pain when you acceletate. easy to hear right at the top of the engine. Put a screw driver on the Cam box and get your ear to the top of the handle and listen.
Big end = you can feel the lack of power, usually comes with a weakening engine real bad at start updissapears on the overrun. makes em smokey too with unburnt diesel. usually its only one cylinder iknow they can all wear out together but usually one gives up first.

Diesel crack = that mid range just as you put your foot down gently burst of rapid ak ak ak. You tend to hear it in cold just after startup healthy engines.

Effect of chip = i cant help you one little bit here Sorry, accept you probably are ageing your engine faster.

I know from my trucks that after the dealer turned up the Horse power at the injector the engine did make a much stronger tappety cracky noise for the whole month till the engine blew up.
PS it was german too.

But probably just the sound of more fuel being squirted into the combustion chamber.