Little 1800 cc on a 1975 Fiat Spyder? If it's the same motor as my 1974 124, it's a DOHC interference design with dual carbs. That baby not only had loads of top end power, it really growled nicely.

Anywway, I suspect you are referring to the air pump that connects to the cam on the Fiat (a frequent cause of timing belt failure, by the way, when it seizes and forces the cam to strip the timing belt.) The B23 and B230F Volvo motors use exhaust monitoring to deal with emissions, not sure of your B21 motor. Basically if you have an 02 sensor on the downpipe, there's not much you can do beyond keeping the engine in good shape, and possible removing AC if you have it. Removing the power steering is also an option but I don't see it as that much of an advantage over the price you pay in the parking lot.

Scherm, Halifax