Problems with Escalade 07!!!! Need help!!!!!

hello everybody!

I have an Escalade 07, AWD.
This SUV is a nice one, but now have several problems with it.

First, engine started making noise, when I started it cold. I changed the plugs and air filter, noise dissapeared.

Then, it lost torque and power. When I press the acceleration pedal, it does not speed up, and does not react on pressing. After several seconds, it starts running, and speed raising, looking everything OK, but then suddenly looses its torque and reaction again.

Why I ask assistance- I am living in Europe now, and here nobody can tell anything about it. The dealer (NY) where I bought it, recommends me to bring it back.

Did anybody have something similar ? Any ideas?

I would highly appreciate Your help.

Thanks
Eugene