Date registered: Jul 2006
Vehicle: 1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
Location: NW Arkansas, La Jolla CA, Hong Kong
Mentioned: 6 Post(s)
Quoted: 157 Post(s)
You have mentioned a -100bhp reduction in power, that kindof power loos can only come as a result of serious restriction in-or-out.
Normally, a soft reset restores the factory defaults, and then the factory defaults degrade over drive time, but 4-6 weeks is not uncommon before even a hep owner "feels" the need to do another soft reset to get the zip back.
However, degrading the factory defaults that result in a - 100bhp loss, something has to be very wrong - wouldn't be the fuel supply, or the soft reset wouldn't improve fuel pressure loss, the only thing it possibly could be in my mind is a major cat problem - if the soft reset restores the defaults, then the resstrictive cat cause the 02 sensors to lean everything back down (and fast).
I have not had any cat problems whatsoever, so I am not hep on that backend issue - but yes, could be the cause of the major performance loss you describe.