Tuning has nothing to do with compression. Are you sure, the Toyota guys removed your plugs, and installed the following gauge to do the test??? And when you say 8 or 7, what unit are you considering--- kgf/cm3 or what???
A car not giving serious problem does not mean that its fine in all aspects. The compression test (both wet and dry) tell which of the following are failing (or have failed) Rings, Valves or gasket.
And if the figures you post are correct (in kgf/cm), then based on figures shared by driver_guy, i am afraid your engine is moving towards a point of rebuild that would start from rings minimum and further based on engine condition and your pocket as well. Please visit some other workshop or dealership if you still face the problem of oil reduction or reduce pickup.