resonator/silencer removal

[moneytree]

Hi all!
I instructed my workshop to remove the resonator for the exhaust.

This is my story:

After picking up the car, I noticed the sound has improved much, definately louder at pickup, no humming noise, but at high speeds also some additional noise, although marginal,and only when exceeding 160KM/H.

Only now I noticed they have removed the 2 catalyst/filters/silencers and replaced with straight pipes INSTEAD of the resonator: the resonator is still there!

Item 1 and 2 was removed
http://www.realoem.com/bmw/showparts...90&hg=18&fg=10

my question is now

1.) I am happy with the sound, should I still opt for removing the resonator? what would be the effect of cross-mixing these two mods together? any downsides?

2.) should I ask them to re-do the catalyst mod and only do the resonator mod instead?

I noticed these two items are very expensive.

the check engine light came on and I assume it has todo with the sensors for exhaust fumes. any way to get rid of the sensor/light?