Power surging on 1999 Civic 1.5iS V-Tec

From Oxfordshire,

I have recently purchased the above vehicle with just 12000 miles on the clock.
I'm very pleased with the car - it drives very smoothly and returns 50 MPG on a run, which was the main reason for buying the V-Tec Civic as I have a 100 mile daily round trip to work (no fun!)
However, a slightly annoying problem which I have experienced ever since owning the car is a power surge when cruising at between 40-60 MPH. The car feels gutless going up hills in fifth at 60 MPH, but then I will feel a surge which gives the car enough power to accelerate without changing down. The power surge will last about 10-15 seconds, then the engine will 'pull back' again. To me it feels like the V-Tec is engaging momentarily when I think it should be engaged anyway at 60 MPH. Or is this normal to have to change down at this speed to go up a hill?
Has anyone else experienced this?
Thanks.

From Shrewsbury,

SOUNDS TO ME LIKE UR OXYGEN SENSOR IS NAKARD V-TEC ONLY CUMS IN AT 4800 RPM SO U WILL HAVE TO CHANGE DOWN A GEAR

From Oxfordshire,

Cheers for your help Hondatech, I'll see how much a new one is and make the decision then.
Any idea where they are located and whether they will cost much? I'll check the "really useful" Haynes manual for the car, but somehow don't hold out much hope - it seems more concerned with giving you 5 pages on how to change a headlight bulb!

I have recently purchased a 1999 Civic 1.5 with the same power surge problem you described. lease advise the solution & approx cost.