Cadillac Repair: 97 Cadillac Seville sts Coolant loss, cadillac seville sts, radiator stop leak

Question
First of all when i got this car 6 months ago, I found myself on the side of the road 2 weeks later. The car overheated and all the coolant flooded out from under the car.The dealer said they fixed this problem by changing the water pump housing. A week after my info center was telling me that i needed to add coolant, and ever since then every month or so i need to add coolant. Now its even worse more like every 5 or 6 days i need to add coolant but i cant see where its coming out of. The second problem is my car shuts of at lights sometimes. I had a engine code and it was a misfire and a egr valve code. I changed the wires and plugs with platinum 4s. What else can be the problem.

Answer
Check the condition of the lower radiator hose, and if you can get to the water pump, check it for a leak or a visible crack, you can run some radiator stop leak as its probably the only engine additive that actually works. The misfire could be an injector, or carbon buildup in the cylinder, or low octane fuel. Lucas injector cleaner is another additive that actually does what its supposed to do, this will improve the engines efficiency and will probably get rid of the misfire.