hoping someone can help here..
ill try and leave it short as I can so bare with me...

2003 e500. 141000 miles. bought it two months ago. good condition.

when I first got it, I remembered it having a very smooth, even power band from idle to redline.

now it is sluggish in the low rpm, low load area.

not in direct response to the problem, I had replaced a few things for preventative maintenance since the previous owner knew nothing about the car.
spark plugs, wires, air filters, engine and transmission mount, breathers are cleaned and resealed correctly and all associated hoses were changed. new bosch MAF

tested the engine for blow by with a block tester off of amazon. turned out perfect.



i've been watching live data and it runs lean at idle and low load. around 10 percent. STFT stays around 0. you can feel the slack when you drive. the car still has power but has the typical lousy throttle response when more load is added (ie: going up a hill or suddenly pressing the accelerator more)

instead of a smooth gradual increase in speed and rpm, it will kind of rev up a bit to around 2400 is and then theres just gobs of endless power after that. after 2400 rpms, LTFT jumps down closer to 0 and so does STFT.

at idle, theres an ever so small rumbly misfire that if you didn't pay attention, you could miss.(which was like this before the spark plug and wire change btw)

o2 sensor data indicates bank 2 (which I believe is the driver side correct?) runs normal. hovering around .500 ish when a small load is applied.
bank 1 on the other hand does something interesting.. it will hover around .500-.600 ish but then do a sudden dip down to .100 and then swing back up... hover like normal for a bit. then dip again. over and over.

fuel pressure is spot on at 55

cant find any vacuum leaks. thinking maybe compression? idk
Thoughts anyone?

car drives wonderful in higher rpms