2001 Pontiac Aztek noise, in front, also service engine so

I have a noise in my right front wheel. I just had the brake pads changed and its still there. It starts out as a lite thump noise then it whistles, its very annoying, What did I miss
I also had my car checked for the light that comes on, They said it was a gas cap. But thats not it.
It seems when the car is parked on an incline, then I start it and put it in gear the light comes on, but if Its parked flat, I put it in gear and usually nothing happens.
I have seen a recal on the gas tank but it seems not to have those problems, no gas leak,
can you suggest?