The o2 sensor isn't as necessary on the '94 model as people might think. I've been running mine with a set of hooker long tubes and no o2 sensor for about 3 years now. I have however had the issue you are seeing, which was caused by a bad MAP sensor. It's a rectangular piece connected by vacuum hose to the top of the IM/bottom of the TB with a bit of wiring connected to it. When idling the engine is at a higher amount of vacuum than when driving and the timing needs to be adjusted appropriately, which the ECU won't do if it's reading the vacuum reading wrong. If that doesn't work, set the timing again. From what I remember there is a brown wire that needs to be disconnected from the back of the distributor somewhere and then you set timing to 0* TDC reading from the plug wire on cylinder one.