Replaced the fan belts on my car today, mazda 323F imola 1998, after driving the car has got no power, it idles at 700 revs and drops to 500 everytime I put the clutch down.

Red lined first gear and it was like third, the only thing I can think of is that I've knocked a pipe or a sensor off, as it's a fidderly job and me being a truck mechanic I'm a brute.
Anyone had this problem before and can give any tips?

Sorry if this is in the wrong section, move if needed.

Thanks!