engine hesitating
 

Hey guys, I need some help diagnosing a problem:
my 1.8l engine is hesitating around 3000 - 3500 rpms, also I notice considerable loss of power. it alsot feels like "hickups" for a lack of better word. I have checked sparkplugs and wires, have filled up my car with a better gas (because I thought I had water in a gas tank), there are no engine codes yet. Any idea what it could be?

Does it do it only when the car is in motion driving down the road? In other words does it do it when the car is free reving stationary or in a particular gear and speed?