Re: ford focus 1.8 zetec 2001 .Power.
I'm assuming the transmissions are the same as well. The other thing to consider is wheel size, larger wheels (taller overall diameter) will sap more power as it takes more oomph to turn the larger wheels, which also weigh more.
Changing the air filter and spark plugs might help if it's been 30K since it was done. Most shops use standard copper core plugs (good for 25-40K depending on how one drives) unless you specify and pay for a premium plug.
If you carry anything in the trunk/boot, or back seat that you never use and is heavy, remove it. Child seats can weigh up to 50-65lbs alone don't forget. With a few hundred extra pounds on board, performance will suffer, especially if it needs some engine maintenance done.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!