Fuel System

I've been using 93 octane on my 993, but a mechanic told me to use midrange ethanol free gas, 89-90, higher octane is not available. Is there a benefit for my engine?

What began as a 1971 911T now has a 993 turbo engine and G-50 transmission.  The installation was done by someone who had never worked on Porsches.  Please don't ask.  Okay, my son commissioned the work as a surprise for me, and picked the wrong guy.  It appears the installer constructed a fuel line that runs from the tunnel exit directly to the fuel rail on the right side, using an AN fitting for the inlet connection at the rail.  Picture attached.  The fuel system has suddenly developed a leak at that fitting.  Both the fuel rail threads and AN fitting appear to be okay.  Can you suggest

Car has been professionally maintainrd and service is up to date.  DME relay and idle control valve have been replaced. Idle will hunt fall off and stall the motor. Will start up without any issue and run just fine when warm up.

need to replace steel fuel lines, fuel pump to engine, fuel filter. the delivery line pin hole, return line rusty but seems ok. would like to replace both. where to find-buy steel or replace with rubber-kevlar.any help?

thanks....

M.W.Lafountaine

Is it likely to be the fuel pump?