ok 99 s80 t6.. runs good no codes or messages... i have been trying to trace what seems to be a lack of power.. when you put it to the floor at about 10-15 mph it will down shift and pull nicely and almost loose traction but then immidiatly that pull will go away and just accelerate OK... however if im going much faster then 10-15mph and i floor it it wont downshift and it takes a bit for power to build up im guessing that because it isnt downshifting that the rpm is too low for the turbos to spool up very quick.. when this happends it feels like it should be downshifting but it doesnt unless im at certain speeds... it seems to me that no matter what speed i am at that at WOT it should do what it needs to do to make the power it needs.. i notice it most when trying to pass.. if i go to pass at some speeds its a total dog but at others it downshifts and gets up and goes... I have mounted a boost gauge in the cockpit to see what its doing durring different regimes and heres what im seeing however with nothing to compare it to i dont know if its correct hopefully one of you can help me find out... anyway here goes

idle seems normal at about negative 15-25 lbs... i quick tap on the pedal brings it right to zero for a sec and then it goes back to normal negative 15-25..

if im driving andi can get it to down shift the it will shoot up to about 12-15 lbs but immidiately it will drop to about 5lbs.. its at the same time this drop happends that i feel the power is lost.. almost as if its dumping too much boost overboard. should it not stay at 12-15 lbs of boost while at wot especialy since the RPM's are climbing at this point? or is the computer sensing how much boost it needs based on who knows what and dumping a bunch of boost for best mixture? i have checked everything i can think of including airleaks (visualy) and i changed the overflow valve behind the rediator (right under the manifold) and also i changed boost temp sensor, fuel pump and filter, and visual looked at the turbos..

here are some other things i have noticed... even if i turn the AC off and STC off and come to a complete stop i cannot get the tires to spin (well sometimes it will break traction somewhat if there is unever/bumpy pavement) now im not trying to burn tires all day but its just something ive noticed.. should this car have enough ***** to burn out? seems like it should.. something just seems amiss.. and im wondering why at certain speed it wont downshift and just sits there like a dog and slowly builds up speed.. i test drove another one prior to buying this one and it didnt matter what speed i was at I WENT..

 

I suspect it may be stuck in Winter/wet driving mode (see your manual under transmission) It is supposed to only be effective in drive. Maybe this button is stuck or you have a faulty position switch in the transmission.