I've tried to lower wastegate actuators rate (stock actuators)as MARKSKY said..but Nothing ..NO luck.
I' ve tried -1 mm on the actuators nuts..NO Luck , so -2 mm more (- 3 mm total) still NO luck..NOW my actuators are regulated as stock 30mm see this link http://forums.rennlist.com/rennforum...stments-2.html..BUT Boost is a little lower only in mid range and in lower gears (from 1.0/1.1 drops TO 0.9/1.0)BUT in 5th and 6th gear boost is still 1.1 and the problem is always the same: in 6th gear at 6400 rpms boost drops from 1.1 to 0.6 and remain at MAX 0.6 (limp mode) until i stop the car and turn off the key

 

The strange thing is that boost drops ALWAYS at 6400 rpms (6th gear) exactly...

 

I had the same issue last year and changed the N75 valve along with doing a bunch of pressure tests, but had no luck. After I installed a brand new MAF, everything was back to normal.

 

You should log request boost and boast pressure of sensor. See of the actual is higher then requested

 

The ecu use speed vrs rpm to calculate what gear you are in (thats how 1st is limited) If it is only in 6th it just maybe as simple as the tuner left some stock limits in place. One sure way to do that is to data log and run it on a dyno. If not you can just keep guessing away you may or may not fix/find it. GL

 

Hi . i' ve decided to follow your suggestion and i already have bought a new MAF on ebay...i'm waiting for delivery of it and then i'll try to replace it with the new one...I REALLY hope to have luck and resplve this problem..
Just a question: How do you have understand that was time to replace your MAF to resolve the problem ? ..At How many miles did you replace it ?..and did you use oiled air filter when your prevous MAF has failed ?
Onestly my MAF seems work well ..my car has 40K miles and i've never used oiled air filter ..BUT for only $ 250 i think that to try to replace it is a good job in any case..
I will let YOU know if the new MAF solve the problem of boost as in your case
Sorry for my english

 

Hey I am not as knowledgeable as the above guys ..I would think it has to do with something on how your ECU is programed considering what you are saying ...Good Luck

 

Thanks John ...i also thought this BUT my tuner has already checked the ECU map two times and he says that it is allright so he hypothesizes the problem is some failing sensor like MAF or O2 sensors But NOT having error codes he says that we must do attempts ..
as the flash file is from Rs Tuning /Cargraphic that is a reputable company, before to go to another tuner i'll try with this new MAF hoping to solve this annoying problem

 

My car developed the problem at 30K and I have had a BMC oiled filter since the car was new. I also thought the ECU was the problem first but I had it tested as well before I installed a new MAF. The car has since been perfect for 7K but now I have to replace my original cracked 996 ignition coils and spark plugs since I got a CEL. Good luck!

 

I haven't followed this thread closely but have you data logged the run? you may want to invest in a durametric cable.
markski

 

Mark, There is a saying that fits this thread. It contains horses and water..

 

lol

 

.........??????????? ..."Horses and water" ? I don't understand what you mean ....."Cavalli e acqua" ??

 

Uno puo portare un cavallo al'aqua, pero uno non puo far bere il cavallo se non vuole.

Sara perche ti hanno detto di comprare un cavo Durametric e di registrare cosa succede con il motore quando ti casca la pressione in sesta.

Io lo facio ed e molto interessante vedere i dati. Tante volte uno puo scovare quel che non funziona. Ciao.

 

Thanks Pwarnery ..now i understand well ..and my compliments for your italian...it's sure very better than my english