ok so im grabbin a new sensor, most likely denso. neways. theres diff part numbers for b18b1 and b18a1. i see that all gens of dseries share the same plug as the a1, but not b1. does this mean the plugs are not seperated by on board diagnostics? wut the difference?

 

I dont know what you mean by "separated by obd" but as long as the sensor has the same number of wires it will work. If the connectors are different then swap them. You can even get a univeral o2 sensor for cheaper, which doesent come with the plug and you will have to install your plug on it.

 

As I recall the B18A uses a single wire O2 sensor and the B18B1 uses the "normal" 4 wire.