[NETH]

Hi guys look finding hard to post anything on here.. ive been a member for years I just wanted to pick your brains...
my mate has a 2011 F6 he has had issues with rpm fluttering at like 2.5rpm or really whenever coming onto boost .. on full boost fine.. he since called me saying the car temp was going hot.. after a check on the over flow bottle no coolant evident told him to pull off radiator hose result was oil and water milky sludge water.. mech said cylinder head then found the auto trans cooler F*$ked out.... replaced 2k later he still has the issues with this rpm flutter coming on boosts.. Car is 2011 F6 completely stock 42k on clock... just seeing if anyone has had any issues like this or has an answer for the poor sod.. ive told him to check for vacuum leaks all bolds tightened and spark plugs which he just replaced and he says its a little better.. I told him .. im no mech but having the auto trans cooler go at 40k can not be normal and could be thee gear box? but I wouldn't have a clue would appreciate any help out there at all would be very very thankful.. cheers guys..Neth