I recently got given a GT cam for my standard 1.3 86c mk2f but I haven't yet fitted it as I am unsure if it is any different to the current cam on my engine and weather if it is different is there a noticible power gain,weather it would effect the fuel economy by much and if it's a strait forward fit just remove the old cam and replace with the GT one and weather anything like fuel or ignition timing would have to be adjusted?

you can fit it and use the same pulley and timing, it produces more power so uses more fuel. there will be a noticable difference in acceleration

when refitting the dizzy you'll need to adjust it to get it running right as you would fitting any cam

It is different to a normal Polo cam, just make sure the one you have has '030 AF' stamped on it somewhere so you know it is a genuine GT cam.

As with anything if you increase the power and use it then fuel economy is likely to drop, but at the end of the day it is still a 1.3 so it shouldn't drop by much.

There is a guide to fitting it here http://www.clubpolo.co.uk/forum/index.php?showtopic=217246