Stalling and loud tinny rattle from underneath, also surges when cruise is on

What is your question?

I have a 2004 Ultra and it stalls and looses power from time to time but also has this real tinny sound like a spoon in a tin can noise. Local garage took apart pipe underhood and cleaned sensor noise was not gone but did not stall lately. There is a flapper in the pipe just past where the sensor was he cleaned. Sensor had oil like substance on it. Motor surges with cruise on when you get on incline. Have 2002 Rendezvous and none of these issues. Cruise excells smoothly.