1998 Chevy Tahoe Tahoe WON'T ALWAYS START

I BOUGHT THIS TAHOE AND HAVE TAKEN EXCELLANT CARE OF IT. 3,000 MILE OIL CHANGES AND ALL THE OTHER REQUIRED MAINTANCE.

IN THE LAST TWO MONTHS WHEN I TRY TO START IT, IT CRANKS GREAT BUT THE ENGINE WILL NOT START ALWAYS.
IT MAY NOT DO THIS FOR 20 TO 50 START UPS BUT THEN IT WILL AND I'M AFRAID TO TRAVEL AS I LIVE IN A RURAL ARKANSAS.

I TURN THE KEY ON AND WAIT ABOUT 5 SECONDS BEFORE CRANKING WITHOUT PUTTING MY FOOT ON THE ACCELERATOR.

WHEN THIS STARTED MY MECHANIC GAVE THE TAHOE A COMPLETE TUNE UP AND CHECKED THE FUEL PUMP. HE TOLD ME THE PUMP WAS PUMPING 60PSI BUT THAT THE FUEL INJECTORS WERE DIRTY AND I NEEDED TO GO TO A GM DEALER FOR THIS.
I DID AND HAD THEM CLEANED PLUS THEY SAID I NEEDED THE RIGHT BANK CATALAYIC CONVERTER REPLACED WHICH I DID ALSO.

NONE OF THIS HELPED THE PROBLEM. THE GM DEALER SAID IT STILL MAY BE A FUEL PUMP PROBLEM AND I WAS VERY LUCKY TO NOT HAVE HAD TO REPLACE A PUMP SOONER. I HAD THEM PUT A NEW FUEL PUMP IN AND I STILL HAVE THIS PROBLEM WITH THE TAHOE NOT ALWAYS STARTING. I HAD AN IGNITER REPLACED 3 YEARS AGO. PLEASE FEEL FREE TO CALL ME AT 870-405-5500 THANK YOU, BOB SKIBBE
bobskibbe@suddenlink. Net