Would like to know the HC readings. Unburned fuel either from a dripping injector or a corroded cap/rotor can raise this reading. With the air cleaner off completely, the nuts unscrew from the distributor body holding the cap on unlike any other GM car where you depress the screws and rotate them. It is also very important that the new wires be routed exactly like the originals in the retainers correctly or they will misfire between themselves. Another thing seldom mentioned is the thermostat. If the engine is running too cool, below 195/200 degrees, it will run rich.