The -30 and -70 ECUs are both made by Denso. My notes tell me the -30 has one sh7052 32bit processor and one sh7058 32bit processor in it, while the -70 has two sh7058 processors. One of the processors does the throttle-by-wire stuff, and the other does everything else. It appears that the sh7052 does the throttle-by-wire for the -30 ECU. The sh7058 is twice as fast as the sh7052, has more flash ROM, and supports some extra instructions (sh-2 instruction set vs. sh-2e set). I also have in my notes that the sh7052 was being discontinued, so Denso probably just moved to the two sh7058 processors in this design because of that, not for any performance or ROM space improvement. The throttle and fuel mapping in the two ECUs looks to be the same (based on a spot check in flash-tune). So I think they are plug-in exchangeable, with no observable differences in behavior.