Smelly cadillac engine

I purchased a 2000 cadillac seville STS, 140,000 miles. Good car with couple of issues. Smell like something is burning when i smell the engine after a drive.

I get vibrations in steering when i drive above 70 mph, vibrations increase with speed above 70, its a smooth ride below this speed. Please help, want to be educated before i go to the mechanic.

The vibration may be possibly be from the wheel balance not being correct as a high speed balance may be in order. There is a difference on this from a normal balancing done by most garages.

An alignment check or alignment will probably be on the list with the wheel balance, and a slighter possibility of bad shocks or struts or tires. My guess for the burning smell would be oil leaking from the valve cover gaskets getting cooked on the engine when hot. good luck!