My 03 c32 with 156k miles has developed some very strange symptoms over the past few weeks, maybe someone has seen these before and can help me out.
1) Clakity clak sound when I first start seems to go away after driving a little time. Valve? seems to be coming from the drivers side cylinder bank, but not sure.
2) rpm's will surge and then drop down just above stall, this has happened twice. The check alternator/battery light will come on but will go out once rpm's go above idle.
3) throttle response has acted up twice also. Step on the gas, delay then take off. After a few moments this also goes away.
No check engine light, or codes. Are the symptoms related? Otherwise the car seems to be running normally, I have not noticed any drop in performance. Not sure what to check. I am hoping the forum has some ideas.

when was the last time you did maintenance? In particular your belt?

Belt is about 70,000 miles old. Oil changed 5,000 miles ago. Plugs also 70,000 miles old.

Along with the symptoms, finally got a check engine light, which reset itself after the allotted # of restarts with no faults. Pulled the following codes:
P0175, P0172 Bank 1 and 2 too rich. P0175 Map Sensor. With the above symptoms at the beginning of the thread, is the MAP sensor the problem or just a symptom?

brought it to my tech and he replaced the map sensor, good as new. Also i am not experience the weird 1500 rpm shift that has been talked about, but that could just be because of the reset that the mechanics did while fixing the other issue.

I have changed out my map sensor and have had no further problems.

Thanks for reporting back, good to know