coolant flowing between iac and isc ?

[fixkick]

good qustions
the mod only measure the #4 pressure. or engine load. so the ecu Assumes that all 4 are under same load, and are. 1/4th each.
the whole purpose is to measure load, and match that with proper EGR flow.
in between #4 putts are others, that whole have to travel far to reach the MOD, and before the next fast coming #4 putt (or bark)
keep in mind the mod is tuned to work only on stock car.
the egr needs to work for 2 reasons,,, pass smog.
and more important is to stop PINGING. (Detonation)

i have no way to view the diaphragm valve in the MOD, nor do i need to.... what matters is clear path from MOD to cat, brick.'
the rest is natural. (there is no stopping the any of the 4 exhaust ports from working, only the #4 egr path, can fail.
weather 1,23, have influence, im not sure. and a moot point?, considering what can and can not fail.
i think it will when the cat melts, and the EGR goes NUTS. (a double loss of power)
some years ecu, if code 51 set (usa) the ecu may go to limphome or just go richer to save the engine from ping damage.

for sure the mod is tuned to your car...stock

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in 1999 , the ecu does all this is software ,then opens the egr motor.
no more vacuum junk.