whether it is OBD1 or OBD2, reprogramming the PROM or chip on the computer or "ECU" should be the very last modification.
Why?
the program on the chip is based on what cam, injector, fuel pump, intake, head, header, redline you are using. The fuel map and ignition map are programmed for that engine combination or package. If you order a new program to be burned onto the chip and then you later get bigger injectors or cams, the program no longer is right for that package...it becomes obsolete. It does not fit for the new amounts of air and fuel you are about to add.
The OBD1 chip can have as many programs reburned onto it as you like. Which is great for cost. You don't have to buy a new chip to get a new program. THAT is OBD1's advantage...most beginners mistaken the stock program to be the main advantage over OBD2 and totally ignore or don't understand the reburning aspect. If you buy an $300 reprogrammed OBD2 chip NOW and later decide to get another part that changes the fuel delivery or air delivery, you will have to throw that chip in the garbage or resell it to some other ignorant sucker and buy another $300 OBD2 chip with a new program burned onto it. You cannot just burn a new program onto the current chip you have, unlike the OBD1 ones.
You can order a new OBD1 or OBD2 chip with a program by mail from someone far away that is a guess of what is the best amount of fuel and ignition timing to add or take away for each rpm. You tell the programmer about your engine package and he/she burns in a guess for the fuel map, ignition map, VTEC switch, and redline. Will it make the most power? probably not. The best way to get the program to be done is to take your car to a dyno and have the programmer there to adjust the program on an emulator first before they burn the final program onto the chip or PROM. This way they are making adjustments based on what YOUR car tells them. They don't guess. So your car WILL get the most power out of the program if you dyno tune with a wideband O2 sensor.
Even the best programmers have to change their first "best guess" program to make the adjustments to get the most out of your engine. one mailed in best guess won't cut it.
If you learn anything from this board about ECU's, remember this:
do the ECU mod as your last mod NOT your first mod after i/h/c/e whether it is an OBD1 or OBD2 chip.
AND
if you get a new chip, choose a place which can provide you with proof they will gain a certain amount or your money back. The best ones will be those whio go with you to a dyno with a wideband and do the programing there with you on your car. No guessing involved. This is why the Hondata is such a great system.
BTW this was stated in my ECU article. Makes me puke to retype it all again.