record the timing reading you get and the rpm--check for how far it advances as you add rpm and record-

Most tuning places will be tuning your car for max HP so will want higher octance fuel to run more timing advance------

if you want to tune for street performance and available fuel at your location-tell them that---------and they can work around just drivability at street RPM

Since you had a failure of the chins wall gasket and you used rtv-------maybe you have a oil leak at the corner of the heads/manifold that is running down the front cover and just appears to be leaking there--------

wish you were closer so I could help-------.