we have had Odyssey vans do the same thing with EGR's here , even our shop Van, ive never had to re pipe it and all thatusually the carbon as we see it usually collects under the the base of the entrance of the egr valve to the bottom of the EGR making it usually stick, if stay in a open or slightlly open position, at werst slightlly filling the intake port from the erg to the intake to the egr hole which never really happens cause it does not usually get past the EGR cause its blocked up. I , on my 96 took off the EGR valve, got a new one, took a wire wand and cleared out the EGR thru hole on the lower piping , stood away cranked the van for like 1 sec to blow the remaining trash out and put new EGR and gasket. all was fine afterward.I dont even kno why my van has an EGR valve we dont have that emmisions crap over here, well not tough emmisions anyway, but i see vans here do have EGR's tho. Wuts the deal tho Honda tech USA with the V6 transmission from 98-02? Ive seen some places, we use the american 98-01 honda accords sometimes as fleet vehicles and taxis here. But the main Accord is the japanese market one. i have rebuilt 3 V6 accord transmission a 98 taxi and 2 fleet ones. The thing i see in them are the seals have failed and do not correctlly pressure the clutch drums when the vehicle is 15-30 min after warm up and operating temp.anyway good luck with yur van.