Even my 01 R50 felt quicker with 305k km / 190k miles!
But my 11's performance isn't up to par either at 150k km/ 93k miles . It runs and drives nice but lacks some grunt. I have no check engine light but have a P0328 code stored for a knock sensor on one side. Cleared codes and it's still there so am having either the sensor or the harness to it changed as apparently sometimes a mouse gets in there and chews the harness. No way to tell until it gets opened up and inspected. So, I'm looking for a little power/more economy and I'm doing the following in this order:
Replace knock sensor or knock sensor's harness
Replace original from the factory spark plugs with same NGK Laser Iridium 93759 DILFR5A-11. Never been changed so far and it's due at 100k miles
Install the aftermarket XTP Intake Manifold Spacer everyone here recommends, as well as plenum silicone seals and any other gaskets around this while it's apart. Spark plus swap is a perfect time to do the XTP IMS install!
Replace original never been changed upstream O2 sensors with NTK O2s
I have no check engine light on, I guess because nothing is out of perhaps too wide a set of parameters to turn on the light. Others here have reported swapping out the upper O2s, the ones before the cats, made an instant improvement to economy. Makes sense to me so it's on my list of to-do's. Check out this thread: