Hi, I've posted this on ffoc but was wondering if anyone on here could shed some light on the problem (Rob?)??

Right, My RS has developed a boost problem which has been getting worse over the last few months.

The car has been de-catted, Mongoose system, K&N Gen II + Bluefin.

Basically, when under load the boost peaks then keeps backing off by about 1/8-1/4 of a bar, then peaks, then drops and so on. It doesn't do it every time but is becoming more frequent. One time after this happening the car would only run half boost for the next 10 miles (rest of journey) untill the next morning when it was fine again?! Sometimes changing up a gear or backing off the throttle then nailing it again will make it hold the boost. It's not just a dodgy gauge as you can feel the car pulling then backing off.

Also, twice over the last few months when putting it under load the car has sort of misfired, banged, had no boost then all of a sudden come on boost.

The Bluefin diagnostic came up with the error 'P0234' which means 'Eng Overboost Condition' but I've never noticed it overboost??!! Anyhow, I have re-installed Bluefin to see if that makes a difference and now it's running like a bag of shit, as it did the last time I reinstalled it after fitting the CAT back part of the Mongoose system. It seemed to just sort itself out last time though?

It has been suggested that it could be the dumpvalve (running standard one) or the MAF sensor, but there was no error code for this sensor. If it is the DV I assume the only way to find out is to replace it? If so can the Focus RS run without a DV, will I get chatter??!?!?!

I've yet to take the car out for a proper drive after reinstalling Bluefin to see if it's cured (if it will eventually idle + stop missfiring) the problem.

Any idea's??