Not true.
However, you cannot just run out and purchase a "chip" for a OBDII car (ECU). You would need a conversion harness, to use a OBDI ECU.
ECU tuning, even on a "Stock" motor will show a gain. All though, the gains will be significantly better, if you have work, or bolt-ons done to your car. Hondata is probably the best ECU tuning program out there. It allows more customizable tuning to your motor, compared to a "generic" baseline chip.