I am in to this problem about $400 without any resolution and the 960 goes back into the shop on Tuesday. This is my wife's car and I have been driving it for a couple of weeks and she is right the hesitation is really bad. When the 960 starts up and runs for one minute, all is well, from that point on until the car is 100% up to temp it goes from stall to tire burn to get away from the stop sign. In other words, you have to hammer the gas to get into traffic. According to the shop working on it, they have checked out all of the potential issues and have come up short. Any suggestions other than, get a new mechanic. Thanks

Your cause could be a bad temp sensor? Maybe the connection or the sensor itself. Making the engine a little fuel starved until it is warmed up.
A bad connection/air mass sensor? Getting the wrong temp.readings? That one is easy to test, just unplug it before your next start up, the default program should make it run better. Doing so will cause a code and check engine light.
When you are starting out from a stop, is the trans in first, could it be starting out in a higher gear? Maybe the PNP switch is faulty? When my switch failed, there was no fault code or flash dash light. It just would start out in 3rd gear.
What has the shop done for their 400.00?

DanR 94 964 291,000 miles (57,000 on the new engine)

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DanR

I have a 96 960 that did the same thing. Where I live in Ks it wasn't a problem, just a slight hesitation, but up in the rocky mountains the car would do what yours is doing. According to the Chilton's manual, The oxygen censors are bypassed until the the car warms up. So that is what I figured my problem was. The good news is it go better on its own after about 25000 miles of hard hiway driving.