i have a 96 mc z34 and when my local mechanic scanned it these numbers came up and one of them is not in my Haynes repair manual

PO122---Throttle postition sensor circuit, low input
PO131---Oxygen sensor circuit, low voltage (upstream sensor)
PO133---Oxygen sensor circuit, slow resoponse (upstream sensor)
PO300---Random/multiple cylinder misfire detected
PO410---Secondary air injection system
PO420---Catalyst system efficiency below threshold
P1106---Manifold absolute pressure sensor circuit intermittent high voltage
P1641---Malfunction indicator light control circuit
P1870---?????????

Ahhh, yes. The infamous Transmission slipping for no apparent reason code. There is a kit available to fix this, however, I think it takes a lot of work to install. There is a valve somewhere in the transmission that loses it's hydraulic integrity, and the kit renews that.

Your local (reputable) transmission shop should be able to tell you exactly what the problem is and what it will cost, probably over the phone even.

Looks to me like you need to change a couple parts there: Throttle position sensor and your O2 sensor. Once those are changed, most of the other codes should disappear.

As for that transmission slipping code, I wouldnt worry about it. Fixing it would cost you a fair chunk of change. If the bill came to $500 I wouldnt be suprised.