For cold starts the ECU uses a 'fail-safe' engine start mode, as outlined in the FSM on page EF&EC-34. In this mode a predetermined fuel injector pulse-width is used for the first ten seconds after start-up instead of reading the MAF. Off-the-shelf SZ chips actually have lots of glitches in them and don't properly adjust these pulse-widths for bigger injectors (i.e. they are still set for 370cc), which causes the rich condition for the first ten seconds. I suspect the chip may be causing the other problems too.
