Yes anything running a northstar engine is prone to oil leaks especially if you use a synthetic oil this is because the block is made from aluminum which is more porous then steel so fluids can get past the seals in an effort to fix this gm started pressurized molding in 2000
it should
January 19th.
Where is the leak coming from. Most likely you will need to replace the exhaust manifold gasket which will require removing the exhaust manifold.
The intake manifold.
the intake manifold is what takes air coming from the intake and directs it to each intake valve in each cylinder
maybe you are burning it in you cylanders?
your manifold bolts are loose
Maybe oil (or other fluid ) is leaking from the valve cover gasket (or elsewhere) on to you exhaust manifold or pipe. Or the exhaust manifold gasket may be defective ( this may produce some noise). Have your mechanic checkthe vehicle to determine the exact cause of the problem.
if it's coming out the exhaust manifold it could be a blown head gasket or cracked head.
By "exhaust manifold sensor" do you mean the O2 or oxygen sensor? The only sensor I know of on a exaust manifold is the O2 sensor and if you follow the manifold you will see 2 sensors sticking out they will have (usually) green wires coming from them
Take it to a mechanic.
it's in the down pipe coming from your exhaust manifold. you will have to remove the heat shield from the exhaust manifold to access it