Q7 had thus on going problem 18mnths engine starts no problem ,on acceleration engine dies goes into limp,no lights come on and no codes come up ,all back to normal after restarting ,it has been on diagnostics so many times it might aswell have o e permanently attached,it's had new turbo,new battery,new alternator, crank shift sensor ,egr valve ,fuel filter,air filter,it can happen at any time it won't clear by on and off throttle, or by changing gear in manual, it want go up or down in the gears ,it has had a starting issue which has now been put down to faulty ignition barrel which is due to be changed ,could this cause acceleration problems ? Any ideas