A compression test is a test that show if their is some thing wrong with engine combustion chamber, like crack block, worn piston ring or piston, blown gasket and more. You need to check the spec on the engine.

LSD is the greatest thing to have if you wanna tackle the coner you get more traction on the coner and if you have a rear wheel drive car helps a lot on drifting. It hard to explain how it work, so you just have to look it up