90 festiva running rough, not wanting to accelerate correctly?

[FestYboy]

No mention here of the O2 sensor. Could the computer just be in open loop?

open loop will cause a rich condition (using base tables for cold starts), but you and i both know that there's PLEANTY of power available from a cold start provided all else is in good shape. so asside from major mechanical issues, there's only one other system that will noteably affect power production. (this also goes for a bad ECT sensor that would keep the ECU in open loop).