rediculously heavy steering

hi guys I have a 98 k11 and the steering on it is ludicrously heavy, I know my model doesn't have power steering, but I drove a mates k11 the other day, his was an 02 plate, and the steering on it was ridiculously light and easy, had a look under the bonnet and couldn't see a tank for power steering fluid, so it makes me think the is possibly something wrong with mine as I have to really fight it, any ideas on what it could be or if there is a power steering module I could put on the k11?

cheers for any help