2000e430 4matic 91000miles

last weekend i did the following

replaced plugs with dealer bosch plat's.

replaced fuel filter

replaced oil=filter( noticed creamy stuff in the oil cap)

air filter was replaced 10000miles ago.

after doing this over the weekend, the car drove very nice, lots of power. smooth.

3 days later car feels sluggish and really need to give her little force to accelerate. cant hear any mis-fires. pls advise what could have gone wrong.

starts and sound's fine,

the brake pads are low, could this be slowing the car down