1997 JEEP WRANGLER — ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:MANIFOLD/HEADER/MUFFLER/TAIL PIPE

I HAVE A 97 JEEP WRANGLER. I HAVE A PROBLEM EVERYTIME I START MY JEEP AFTER IT SITS FOR 20 MIN. IT SOUNDS LIKE IT WANTS TO SHUT DOWN AND AFTER PRESSING THE GAS TO THE FLOOR IT FINALLY KICKS IN AND TAKES OFF. I LOSE POWER ALOT AND IT BACKFIRES . I HAVE HAD THE EXHAUST MANIFOLD /CATALYTIC CONVERTER REPLACED AND A BROKEN STUD IN THE EXHAUST MANIFOLD TO HEAD ASSEMBLY. THIS HAS BEEN GOING ON FOR 3 YEARS AND I HAVE TAKEN IT TO SEVERAL DIFFERNT JEEP SERVICE DEPARTMENT. ALL THE SERVICE DEPARTMENTS CAN TELL ME IS THAT THEY CAN'T FIND THE PROBLEM BUT THEY ALWAYS SEEM TO FIND SOMETHING ELSE FOR ME TO PAY FOR . I'M STILL HAVING THIS PROBLEM AND NOW IT'S GETTING WORSE . WHAT CAN I DO? PLEASE HELP. *NLM