You can check your sensors, and most every device with a Mark I, Model 0 Multimeter. And on that device you use its resistance measuring of Ohms to check things out.
The check engine blinking pattern has a pattern for "all clear, no codes". In this case, it will blink on 1/4 second, off for 1/4 second continuously. This sounds like what you saw.
If you disconnect the battery all codes stored, will be lost. When you run the engine, the ECU has a hueristic program that adapts the running routine to what it senses. It takes sometimes just seconds to adapt to abrupt changes that we modder's do.
Are the injectors that you installed of the "low impedance" type? These should give out an Ohm reading of 1.5 to 3 Ohms.
Stuffing injectors with 10% more capacity, or raising fuel pressure up 20% is well within the capacity of your ECU to instantly and competenty adapt to. Now Captain Dumbass here (that's me) stuck 440 CC injectors (a 20% capacity increase) and at the same time he increased fuel pressure to 58 PSI (an almost 100% increase) and my ECU couldn't handle those parameter very well. It still ran a little bit.
I have a simultaneous conversation running with a guy in Washington State, content may be helpful:
http://www.mr2.com/forums/mk-1-mr2-a...-new-post.html
P.S. don't try to get the idle at precisely 850 rpm. around a 1000 will do just fine. The IAC has two screws underneath it, loosen them and you can adjust the IAC quite a bit. The idle adjustment screw on the top of the TB is more for fine tuning the idle.
Its beginning to sound like there's a ray of hope for your engine to make it with the stock ECU.
The point I made about how old and infirm our ECU's are can best be illustrated by looking at how many TV's, Stereo's, Computers, cash registers, alarm systems, radios, etc that were made in the late
80's AND are still working and in use today.