1998 Volkswagen Passat 1.8T 20 valve exhaust problem?

Hey, so my Passat's muffler just fell off.... so for the sake of any other part of my exhaust falling off and hitting someone behind me while i drive. i lifted up the car and checked out the whole exhaust system. basically everything past the downpipe is pretty much ****... My question is, if i take off the secondary muffler and catalytic converter, replacing them with a straight pipe and new muffler. would i have to tune the ecu any for the sake of the O2 sensors?? i ask because its a turbo'd engine and idk if this would throw off the fuel management. in otherwords, blow my engine.