I was told by a tech that having your oil pressure gauge pegged at 70psi (i.e. after warm up) is symptomatic of the pressure sender shorting out inside. There could be issues involving the low pressure light related to this too, if your sender unit is bad.
I had a similar issue with mine. Would peg at 70psi on startup, then drop to around 35 when warmed up. When revving the engine agressively, the presure gauge would go lower (as opposed to higher) and even flash the low pressure light. Under just normal light throttle presure (cruising) it would load up with the throttle normally, hitting a high of 70psi at higher RPMs. it was the sudden revving that caused it to operate strange, in my case.
The tech though it could just be a loose connection, and it was -- so he was able to fix it for free when the car had it's oil change. Thing is, though - I wasn't watching him work on the car when it was fixed so I don't know where the "loose" connection for it was. Likely at the back of the block where I believe the sensor is, but who knows?