Nissan Repair: Missing ECU, mass airflow sensor, intake leaks

Question
Hi, I have a 1990 Nissan Maxima manual transmission. Two years ago the ECU was stolen but the engine did not show to miss at all this part. Basically, it kept running as if the ECU was still there. In August 2008 I begun a partial overhaul of the engine (i.e.: serviced the heads, replaced two injectors and serviced the others and so on...). I have closed the engine, cleaned the electrical circuits and replaced the old hard rubber hoses with new ones.
The engine starts, but upon warming goes slowly down in RPM untill it stalls. If I try to drive it, it looks like the engine does not deliver power and I need to give much more gas than I was use to before the overhaul. While driving sometimes surges and if the RPM go too low it doesnt react giving more gas automatically, but stalls.
It would be great if you can give me your opinion on this matter. Right now I am still missing the ECU. Do I need one now or the problem might be elsewhere? Thanks!

Answer
Anto,

If the ECU was missing the car would not run.  The computer box you had stole was for something else.  I would think the reason your car is doing strange things is due to the mass airflow sensor or the like.  Other than that, make sure the timing is on the mark and that you do not have any intake leaks like a loose hose or a sucking gasket.