P0401, two shops and the Buick dealer cannot cure code.

Thanks for the info. There are no clogs on the upper side. All lines hard and soft checked or placed. TB clean, new egr hard line to intake, dealer check all passages, no blockage. All mechanics and shops old guy 3800 himself said huh! I will remove intake lower and see what is down there. Still do not believe that is the problem. Street guy said O2 sensor was his problem. Diag said no bad sensors. They had it all day and could find a problem? All that is left is replace map, maf, and O2 until something gives. Sounds like the wrong road to go down. Will see if anyone else has a thought. Grump out.

ok.well i have seen that code(egr insuff.flow detected) more than you can imagine.and it always turned out to be a vacuum leak,pressure sensor, egr valve,and most of all carbon build up.i'm sure one of or both shops and the dealer hooked up a REAL SCANNER with live data and should have found it.but,maybe going to start guess until it's found.i did read somewhere that a map sensor was someones problem throwing that code,and it was the last thing they tried,and it fixed it.good luck with it,and post findings.