Removing the O2 sensor

Hi,
I had a slight prob when fitting my new manifold in that the instant gasket stuff went a bit wild. It blew white smoke then cleared itself its now a bit sluggish. I disconnected the o2 sensor to diagnose and it ran fine so my question is this.
What effect will it have if I run it without the 02 sensor until I get a new one and poss a new cat?
I had an old 206 and it ran for thousands of miles without 02 sensor as the previous owner cut the cable.
Could it be just the sensor\cat?
Anyone ever tried the cat cleaner from halfords?
Thanks

If you run the car without the o2 sensor you will burn alot more fuel so will get less miles per gallon, you will also have an high emissions reading.

I've used cataclean straight into to the tank and it worked the first time and got the car through mot, the following year it didn't work so ended up replacing the manifold cat, underfloor cat, second o2 sensor, new plugs, ht leads, oil and filter change, air filter then cleaned the fuel injectors, it then passed emissions on mot.