ISX smoking & sneezing

[Dan]

Hi everyone I'm new here but find it very educational. Anyways I'm from Australia WA, were running a western star with a isx was at 620 when it was on triples up north now we do only logs & have derated him I'm sure to 515 or 500 still goes hard. Performance has been erratic lately some days it pulls like a trooper others well? Should of stayed in bed. It's started to make a prounced whistle I think from the air intakes at idle, it's also sneezing coughing or hiccuping at times right were u need it at say 1500 on a real hard pull it I'll sneeze & whammy it's all over you have to quickly find 1st & then into it. It's also smoking a lot especially when ur going easy on the pedal then u get into it & look in mirrors & holy cow I'm rolling coal so to speak. It's a 2007 EGR only and gross were at 83.5ton so not overly heavy fuel has sat steady on average 1.3km per litre regardless so when it was up north and grossing 170ton & set at 620 in 45degree heat it was getting same fuel????? Dunno how they figure that but it's true we've had zero fuel savings derating him, but saved squillons on tyres & who knows maybe even the engine will live longer. It's got 630.000km. I'm thinking EGR valve may be sticking? It's going to cummins here in bunbury today just to get computer hooked up any thoughts on directions I should go ourselves regarding this a lot of people are saying it's fuel cause it's black smoke but reading on this site I'm not 100%sure. Anyways sorry bout big story