Check Engine light Beacause Wheel Size and K&N Filter

I recently had a check engine light come on my 06 Mazda5. I have a k&n air filter replacement and I had the dealer switch wheels with a Mazda 3, At Delivery. I went from the 17" wheel to the 16" wheel because of the ride preference. There is a slight difference in circumference about 8 tenths of one percent. The dealer said the Check engine light was because of the different circumference in the wheel and that threw off the Check Engine Light Via a trans axel speed sensor. They also pointed the finger at my K&N filter replacement and mentioned oxygen sensor. The service writer said that they reconfigured the ECU cleared the CEL and Gave me Back my 5 covered under warranty. But.......... Gone is my ZOom Zoom. The car does not have the same pep. Just like it did with out the k&n Filter. This First Check Engine Light happened a year after running on the 16" wheels and K&N replacement filter. What did they do to my Mazda 5 and how do I get my pep back? I almost want to look and see if they stole my filter replacement and swapped it with a stock one!

Any Help or Ideas?

Thanks Ted.

hmmm. ive never heard of a different wheel size throwing a CEL.
ppl change tire sizes all the time, ie, they go with 205/45/17, instead of a 205/50/17 tire, cuz its more common, and cheaper.
 
the only thing i can think of is you K&N. is it a wet filter? if so, maybe some of the oil came off, and clogged up the MAF.
 
also, K&N filter WILL NOT void your warranty at all. they are designed that way. i believe it even says that on the box.

Yes the oil filter is a wet filter, but the last time I changed it was in the summer. Why, how and what did they reconfigure on my ECU and why is it affecting the performance?

Thanks Ted!

i cant see them reconfiguring your ECU.
clearing the CEL, yes, reconfiguring it, no.
 
maybe the adjusted your air fuel ratio.
a lean mixture would result in better gas mileage, and less hp.
a rich mixture would be the opposite.

did you swap the rims back to the stock ones at all??
 
 

oh, i just thought of something!!
 
try disconnecting your battery for 20 minutes or so.
(even over night if you want, just dont forget!).
this will reset your ECU.... and MIGHT fix your problem

Just as a point of information, I ran the K&N panel nearly 20K miles before replacing it and even did an airbox mod.  It never threw any CEL's.
 
If you reset your ECU, as Adam suggests, and the CEL light comes back on later (it isn't likely to right away,) you may have to remove the MAF and clean it.  You want to be EXTREMELY careful if it comes to that as they are very sensitive and damage easily.
 
I've cleaned mine and here's how: Do NOT use spray or compressed air.  This is guaranteed to destroy it. Use 50/50 rubbing alcohol and a very light touch w/a Q-Tip.  The bulb that's to one side (it looks like a drop of old school glue) is the target.  It hangs down on two delicate leads and is hard to get all the way around because of the plastic housing, but can be done. 
 
I stress this again, if you don't want to have to buy a new MAF sensor ($80-$140) BE EXTREMELY CAREFUL HANDLING IT AND CLEANING IT.
 
'Nuff said.   Good luck.