In my 89 Formula 350, when do I need to upgrade my stock ECU with a chip or a new stand-alone unit?  I want to start putting in some of the more basic bolt-ons like ... headers, cat-back exhaust, and also something on the intake side like a K&N unit, throttle body air foil, mass air flow sensor, or even having the TPI plenums grinded.  I also assume that I will need to beef up my fuel system since I have some ideas for the air flow, but I don't really know where to start there if anyone can help me with that too.  But my main question is how much modding can my stock ECU handle before it doesn't know how to handle the extra air and fuel??  Does anyone have any suggestions for chips or entire ECU's, if that is what I need ???  

I have the same car and the first performance upgrade I made was to install a HyperTech chip. It required installing a 155 degree thermostat. Most basic upgrade ECU chips alter the timing advance and coolant temperature at which 1 fan cycles. There is a coolant temperature switch in I believe the passenger side head that controls the other fan. You can get these at Summit. I would recommend this upgrade at the same time as the chip as these engines run hot with stock set up and you have to drain the coolant to change the thermostat. You'll also HAVE to run premium gas if you don't already. I added Edelbrock headers, Walker Dynomax cat back exhaust, SLP cold air induction and intake runners and air foil. 89 should have a mass airflow sensor. This will take care of the small amount of additional fuel needed. You can also get an adjustable fuel pressure regulator from Summit. Years ago I had the heat sink inside the mass airflow sensor ground down by TPIS to increase airflow. Summit sells a high flow adjustable mass airflow sensor but I don't know much about it. If you keep the stock cam this chip should work well. I had a custom chip burned by Superchips when I installed a Paxton supercharger. Basically the stock ECU will work as long as you keep the TPI. Dramatic changes such as a cam change or the addition of a supercharger and/or high flow heads will require a custom chip. If you decide on a cam change go no more than 224 degree intake duration at .050 as the TPI is designed for low and midrange torque production.  

Wow, thanks for the info.  You have an 89 formula 350??  Do you ever take it to the drag strip.  I'd like to take it to the strip and get a time with it stock like it is and work it down from there.  You gave me a few ideas, so thanks!!