Is your check engine light on? YOu can have the codes read for free at any Autozone. Post the codes back on here and we can help. If you are past 100K and you haven't changed the sensors, it is time. I think www.roverconnection.com or www.roverparts.comwill have the best prices. If you get into the generic ones, you will have problems. Have to solder, heat shrink and liquid tape the connections, and even then, might be faulty from the get-go. It is worth the $$ to get one's with the connectors.

I replied to your other post, and you have AEL with a 98...

I would have your battery and alternator tested while you are there, its free too...

 

Soldering the connections and heat shrink would take a mere10 minutes/per O2 sensor. Actually, if the sensor is compatible (besides the connections), you should be able to work the pins out of the originalconnector, carefully open them up with a small screwdriver where the wires are crimped, then recrimp onto the new O2 sensor leads. Then, you would not have to splice/solder any wires. It would be perfectly stock in appearance. Ensure sensor compatibility first.