You will need a intake manifold set and possibly a plenum gasket set.
Because it's leaking somewhere. Other than lines in the cooling system, head and intake manifold gaskets are a possibility.
Year, make, model and engine info would help but, the intake manifold gaskets are known to leak coolant on many Chevy/GMC engines.
On a 1999 Camaro, the map sensor is located on the back of the intake manifold. The intake manifold is the series of tubing that distributes the air coming into the engine.
The egr valve should be coming off of the exhaust manifold.
the inlet manifold could Be leaking so check the gaskets or the injector seals
it sounds like your exhaust manifold gaskets are leaking or you half a hole in your Y pipe
You may have bad head gaskets when,you are losing engine coolant and you don't see any leaks.you see a white smoke (steam) coming from the exhaust pipe.you have a sweet smell coming from the exhaust pipe.you see air bubbles in the radiator coolant with the radiator cap off and engine running.
Probably a gasket or seal. Could be the rocker cover gaskets, intake manifold gaskets, or end rail seals. Have even seen the oil pressure sender leak and spray up onto the manifold. Get everything cleaned up real good and you'll be able to see where it's coming from.
The oil leak is coming from the valve cover gasket and leaking onto the exhaust manifold, the rubber valve cover gaskets get hard from the engine heat and start to leak, you will have to replace the rubber valve cover gaskets to stop the oil leak
im having the same problem with my 99. i know the V6 engines have problems with the intake manifold gaskets. only problem is my leak is coming from somewhere by the reservoir as well. check the gaskets and see if it is leaking around them. if not...hop on the troubleshoot train that I've gotten onto. good luck bro, they are great cars. i love mine.
Also losing coolant i believe. That would most likely be head gaskets. And hopefully only that.
You may have bad head gaskets when,you are losing engine coolant and you don't see any leaks. you see a white smoke (steam) coming from the exhaust pipe. you have a sweet smell coming from the exhaust pipe. you see air bubbles in the radiator coolant with the radiator cap off and engine running. you see a milky substance collecting on the engines dip stick and/or engines oil cap..