Sputters, Stalls

Hey all.Car sputters, bucks stalls and finally cuts out when under load especially on hills.This only happens in winter below 0'C. Originally it happened 3 years ago at 1'4 tank, then 1/2 then 3/4 and now between 3/4 and full. Only code I get is egr P0401.The egr pipe to manifold was split/rusted when I got it and fumes were deadly in the car. Unable to get the old one off without major work I cut and blocked both ends and as I said it worked fine 'till winter. I have cleaned the MAF sensor. Is it the possibly the IAT sensor?
Thanks

It might be helpful to monitor fuel pressure and check the ignition system. Spark plugs with worn electrodes/wide gaps can misfire under load. The same can occur with failing plug wires.