Vauxhall Brava has lack of power

[john.stuk]

I have a 4x4 ex post office Vauxhall Brava crew cab with 2.5 turbo diesel engine. Are they all so flat?
I have spoken to two people that tow with them, and they consider them OK.

I wondered if the post office has a power limiter of some sort or has the timing been set wrong for the fuel pump when cam belt changed.

HELP please, need to sort this out. It cost me £3k on ebay and struggles to get to 70mph.

I want to pull my race car with it!