VW Golf 1999 Loss of power problem

I have a 1999 VW Golf TDI (115bhp) which has suddenly lost power. It is especially noticeble when climbing hills ie I can be happliy doing 80mph along a motorway, and I will soon be doing 65mph if climbing a minor hill. I have had the car for 2 years and it always maintained 75-80 when climbing these same hills on my way to work. Any advice would be much appreciated.

It is also slower picking up through the gears. Don't know if the TURBO isn't working?? It doesn't seem to kick in like it used too.

Most common failure causing those symptoms (you didn't mention tons of black smoke) would be the Mass Air Flow sensor. It is located in the air intake pipe just after the air filter housing. Proper diagnosis requires a scanner, but if you want you can pull the 5-pin electrical connector & drive, if the performance improves (it won't be perfect) the sensor is bad. This will set a check engine code that will need to be cleared, most larger auto parts chains can do this for free.

Most common failure causing those symptoms (you didn't mention tons of black smoke) would be the Mass Air Flow sensor. It is located in the air intake pipe just after the air filter housing. Proper diagnosis requires a scanner, but if you want you can pull the 5-pin electrical connector & drive, if the performance improves (it won't be perfect) the sensor is bad. This will set a check engine code that will need to be cleared, most larger auto parts chains can do this for free.

Thanks for the advice boschmann, replaced the Mass Air Flow sensor as you suggested and the performance is back to normal. Thanks again for the advice.