Pontiac Repair: 1985 Fiero w/rebuilt 2.8L Check Engine, aldl connector, flash pause

Question
Let me first say thank you for your time.  
I have an 85 Fiero with a rebuilt engine with
mileage of about 4000 on it.  We had a problem
with the engine after about a year and the mechanic
that installed it would not honor the warranty.
So we sent it 300 miles away to have it fixed. It
runs great, but lately, when you go over 55mph, the
check engine light comes on.  We don't have any Auto
Zones or the like in our area.  Does the light
coming on at a higher mph give you any clues to
what could be wrong?  Thanks

Answer
Could be an EGRvalve problem or its running to rich or lean. Actually it could be alot of things. I assume that you dont want to take it back to the guy that put the motor in, but is there another shop in town you could take it to or the dealership?
You can get the codes yourself if you want to. all you need to do is jump across terminals A and B of the ALDL connector. Its the connector that I would plug my scanner into. It is usually under the dash on the drivers side but it could be in the center console on your Fiero. When you find the connector, use a paper clip or a piece of wire to jump across A&B(they will be side by side in one row of terminals, not one in each row). If you jump across the wrong ones, dont worry about it, you wont hurt anything. So when you do find the right ones, the check engine light will start to flash with the key turned on but not running.
The way you read the codes is like this. Count the number of flashes, there will be 2 sets of flashes, the 1st set then a short pause then the 2nd set of flashes.
This is the sequence for a code 12: FLASH-pause-FLASH FLASH
Code 21 would be: FLASH FLASH-pause-FLASH. See how it works?
Each code stored will flash 3 times and then go to the next code. There will be a code 12 that flashes first then whatever codes that are stored because of the problem and then a code 12 again. If you get the codes and then can let me know what they are I can help you farther. This is very easy to do, it just sounds hard. All the codes will have 2 numbers like 12, 21, 54, 66, etc.
Good luck and feel free to ask me again if this doesnt make sense or if you get the codes.