CEL codes thrown on '98 323IS

[byrdman454]

I recently changed my single 323 exhaust with an exhaust from a M3. I am reading the mixture from one bank of cylinders and plugged the other. This has been done numerous times by other 323 owners.

I completed the job, but threw some codes. Here they are:
I hooked up my diagnostic tool and had 2 codes. One is P0135 O2 sensor heater circuit malfunction (bank 1 sensor 1) and P0141 O2 sensor heater circuit malfunction (bank 1 sensor 2).

Does anyone have any ideas about this heater element malfunction? I can't imagine both sensors going out at the same time. The car has 91,000 miles and I doubt the sensors have ever been changed. Is it OK to drive the car like this while I figure out what to do? It seems to run great.

On my Porsche, you can buy a generic Bosch O2 sensor and just splice the correct connector on it. Is that possible with this BMW? Does anyone have a P/N? What about the cheapo generic eBay ones? Anything else to try before I buy? Can the O2 sensor connectors be hooked up backwards? I did have to disconnect them when I removed them from the old pipe.

Thanks