I am having trouble interpreting the ECU rule for ITCS. On GCR page 331 the rule states" Engine Management computer mat be altered or replaced". On page 334 the rule states " Engine Management Computer may be altered provided all mods are done within original housing". Does this mean we must stick with OEM ECU and can only replace it with another OEM ECU and/or only have the OEM ECU reprogrammed if no vendor makes an ECU that fits in the stock housing??? I am running a Ford Escort GT ( Mazada 1.8 BP ) engine, 1991-1995.