I own a W reg Mk4 Golf TDi (90bhp). The car is very slow, it struggles up hills and is generally no fun to drive. It's never been a fast car but i'm sure it wasn't this bad when i got it a couple of years ago.

I've read up on the internet and found that several people have reported a loss of power problem with these Golfs, although most report a sudden loss of power which is rectified by turning the engine off and restarting it. This is not the case with mine, it's just permanently underpowered.

I've booked it in for a diagnostic test at a local VW garage (Myers Motors in Beckenham) tomorrow but don't really know what to expect.

Can anyone tell me what the diagnostic test will actually show? Will it show what Bhp my car is actually producing or will it just come up with an error code? Lots of others seem to have spent fortunes at garages fixing these error codes only to find out that there's no real difference in the perform\nce of their cars! Any tip on avoiding this?

I really want to get the car re-mapped, but it seems pointless until this problem is fixed. It is an oldish car and has done 110k plus miles after all.

Any advice greatfully accepted, as you can probably tell, i don't have a huge mount of experience!