Tow Vehicle Repair (EGR Valve) - hey it tows the antique!

[RoadsterRich]

Sorry it isn't an antique car question, but since it is my tow vehicle it does sortof relate. It is a 1989 Suburban 1500SLX with the 350engine, and 4x4. The transmission and differentials are rebuilt. I bought it recently with the differential shot, it sat for 9 months prior to my purchase without being run or obviously driven. (Drivers side bearing had cut about 1/8" groove into the axle and bits were strewn throughout the differential.) I did the major routine maintenance things (and had the differential professional rebuilt, everything except for the housing is new, including the axles). I've put 600 miles on it since it was redone. Every now and then (4 times so far), the Service Engine light comes on briefly. The error is a '32', which says it is for the EGR valve. I checked the vacuum lines, they seem good, the EGR valve itself seems to work as expected, and the solenoid for the vacuum seems to be fine too. I'm not sure what else to look for. Another side note is that the car runs great at idle and at highway speeds however from about 32mph to about 34mph the engine will surge and slow down, like you were pushing the gas down and letting it up. Speeding up to 35 or dropping down to 30 and everything is fine again. Other than these two issues it seems to be running fine. Any suggestions as what I should search for? Might it be the O2 sensor? Not sure where to look, it is newer than what little expertise I have covers, so open to suggestions.

On the positive side I love the Suburban, looks great, drives great, handles great. Couldn't recommend them enough to folks, though had I the budget I would have gone for the 2500, this will do for what I need living in flatland (Florida), and only towing just under 6000lbs including enclosed trailer and car. It does have the 3.73 rear end, some have told me I should have replaced it with the 4.1, however I bought it and the trailer together and it has 130,000 miles on it, much of it towing the trailer. Seems like it should do the job for me until I can affor something bigger and badder.

As always, thanks!

Rich