reduced mileage after new cap rotor and PCV valve

I replaced my cap, rotor, and PCV valve with Honda parts
about 3 weeks ago on my 98 civic 5spd. I noticed a big difference in
acceleration. So I gave myself a week to enjoy the
newfound peppiness, and then started driving normally
again. My mileage is definitely worse than it was before.

Before I got easily to 1/2 tank (23-25 liter fillup) and
the odometer would read between 270 and 330kms depending
on the driving mix. (usually about 50/50 city/hwy)

Now I get to about 260kms tops on the same amount of fuel.

It is a little cooler out now than in summer, but its
still above freezing, so the mileage decrease experienced
from the cold should not be a huge factor yet.

Any bright ideas?

t