Vehicle Speed Control Related Problems of the 2012 Volkswagen Touareg

Vehicle Speed Control problem

There has been a substantial change/decrease in the performance of my 2012 Touareg tdi resulting in significantly reduced fuel economy: previous avg fuel economy was approx 27mpg and is now barely averaging 16 mpg. Noticed continual decrease in car performance after taking my car in for general maintenance to garcia vw dealership in santa fe, nm on the following dates: 3/6/general maintenance (air/cabin/fuel/adblue maintenance/ and tire change) 4/17/replace a faulty radio which suddenly failed (dealership had car for 8 days) 6/7/clean up ad blue fuel spill in the rear spare tire compartment the engine now runs significantly louder and is revving up and surging at intervals. In addition to the substantial drop in fuel economy, the average speed/mph has been locked at 13mph and dropped to 12mph on June 1, 2018. Change in engine behaviour: -engine runs louder and is revving up when idling,accelerating, breaking,downshifting -sounds like the fuel injection is sluggish when accelerating -steering wheel feels sluggish when turning right and accelerating through turns. Vibrating sound when turning. -starting ignition: longer pause for ignition to start after turning the key and foot is on brake. -suspension: suspension of the car rocks back and forth when braking and sounds like there's a tank sliding/ shifting in the rear when coming to a stop. When I initially heard this sound I opened the trunk/cargo area for the spare tire and found dried ad blue spilled all over the cargo area including dirty rags which had been used to wipe up adblue and stuffed in the bottom of the trunk. -air conditioner is emitting a very strong nauseating yeast odor that will not go away and isn't cooling efficiently. I havent authorized or approved any updates modifications to the vehicle the 3. 0 liter gen epa/carb modifications: I suspect vehicle tampering.