My 16 hp briggs . When I mow on an angle or slope towards the carb. The engine starts to die and really heavy blue smoke pours ot exhaust.I checked in the air filterawhen this happens and there is fress oil there .Oil level is fine.On the flats it seems to work good.I've adjusted the valves since and no change.I was told to check for leaks as he said it needs a vacume and the only leak so far was the dipstick tube witch is also fixed and no change. Any thoughts?

Also can I stream line my searches ?
Thanks.

Check your crank case ventilation tube , I would think that that is where your problem lies since you are experiencing fresh oil in the air intake.

Yes I Have A Thought, If You Have Oil On Your Air Filter, Then You Have A Bad Breather Assembly, Go To Your Nearest Shop And Carry Your Engine Model, Type , And Serial Numbers, And Purchase A New Breather. This Should Fix Your Problem. The Breather Is What Has The Black Tube Running From The Side Block Of The Engine To The Air Filter Housing.