in all honesty i've never had a reason to own a leak-down tester. a compression tester is all i have and i think it was like $25 at the parts store. i would just start out with that and make sure you have good compression on that side where you had the loose bolt. i would do that only because i'd be worried about the head gasket having blown out around that loose bolt. that could cause major headaches. i might also be the source of your exaust. i think it might be worn valve 'stuff' and like said above, leave it be and drive the car! some leakage is normal.