civic vx issues! help!

[silversol]

i just finished my cx to vx conversion i have no check engine lights. i did do the timing belt/plugs ect. but when the car is driving at cruseing speed it will slightly lose power i assumed it was lean burn and will start to slow down and when i give it a little gas it will do a slight sputter then speed up. also the gas mileage is not what i had hoped for it looks worse that the cx engine i dont not have exact numbers yet. but i am thinking it may be time of a 02 sensor! but i am not looking to spend 200$ on one. does any one know of a cheaper alterative? thanks for you help!

[silversol]

ok i just when to the gas station and refilled the tank. i forced in 2.746 gallons after going 123 miles so thats right a 44mpg and thats all city driving. but my gauge has been acting funny and maybe its just makeing me paranoid!