HI, mbtjc, joep and Scott, thanks for the reply.

After reviewing the replys, all the Bosch 4-ground plugs were being replaced with the original single normal ground electrode Bosch Platinum plugs. But rough idle conditions still around, but with a better throttle response. I

Well, my mechanic had told me that he will expect several broken bolts will happen if decided to do it......I just hesitate to proceed.

As Scott recommended, why pull so many 'ITEMS' apart for just those 8 vacumn O-Rings --- if a complete Head job MAY solve these rough idle and guid seal problems.

Scott, the MB mechanic did scope the first time before did the fuel injector job --- here's the story.......

After the fuel injectors' replacement and timing back to normal, the idle seems gone 90 % at the moment we test drive and the first 3 days of driving.

The 2nd time he scoped the car and said two injectors were bad and replaced with warranty -- but this time, no matter what he had done to 'tweak' the car -- rough idle still there. I forgot to mentioned that two rubber intake hoses - R & L - replaced. Also, 8 new injector holders.

That's why he 'recommended' the center intake manifold plenum O-Ring job ? It's very obvious that he just 'guessing' the next solution AT MY EXPENSES.... He didn't even mentioned those easily wear out items -- like vlave guid wear, cam conditions good or bad on my car ..... because I ask him what did he found out other bad parts needed to consider before I O.K. the job. The parts and labor caused me around $670.

Later, I will drive the car to either MBI inc. in Portland or local MB dealer at downtown Portland to take a look and get an estimate and posted the results on this message board --- so others knows the pros and cons. Thanks again for these great helps from all MB friends.

Now, any more suggestions besides a complete valve job or should I replaced with a new or used rebuilt head ????


Regards.