Here are the issue I have

Original Owner ML320 1998 with 163000 miles on it. Serviced every 10k with Sythetic Oil from beginning. It was one of the first.
with Pages and Pages of Factory recalls.

I had the problem of engine not shifting in long trips with hot weather during long highway driving. (Like some others past posting)

http://www.peachparts.com/shopforum/printthread.php?threadid=69113

http://www.peachparts.com/shopforum/showthread.php?threadid=84290

http://www.peachparts.com/shopforum/showthread.php?threadid=86170

It has been a while that I have not run to that problem. I didnot change anything. Dealer could not find a flaw.

I also ran into problem of low oil light on long trips.
I checked oil with the dipstick. Sometimes it shows low sometime is normal.
Puzzeled by that one??
http://www.peachparts.com/shopforum/showthread.php?threadid=59370

So far I have not run to that problem. I didnot change anything.

Recentely My engine light came on and off.

The mechanic told me today I need to change the Mass Air Sensor.
If I don't change it. It gone ruin my catalytic Converter.
Is that true?

What does these code stand for P0173 and PO170?

How do you know your MAS need to be changed?

So far on the ML. I just do the A service at the dealer(every 10k service).
I don't do the B service anymore. (B service they donot do anything it seems except air filter for AC).

So far I have not change anything major(i.e Spark plugs, Fuel Pump, Transmission oil, and Coolant and etc....) The dealer has never mention you need to change it.

How do you know when to change Spark plugs and coolant?

The only major changes were the belt, oil pan, o2 sensor, gas sensor.

Do you recommend to change anything proactivley? or
Should I drive it until it failed? Then change the MAS, Fuel Pump, and etc.......


Thanks in advance,