2004 VOLVO VNL Engine And Engine Cooling Problems

MY VOLVO TRUCK STARTED HAVING LOW POWER PROBLEM AFTER A CERTIFIED VOLVO DEALER REPLACED COPPER CUPS ON IT. TO FIX THAT PROBLEM, I TOOK THE TRUCK TO ANOTHER CERTIFIED VOLVO DEALER, WHO REPLACED EGR VALVE,WHICH WAS UNDER WARRANTY. ACCORDING TO THEM, IT WAS SUPPOSED TO RESOLVE THE PROBLEM, BUT IT DID NOT. IT STILL HAD LOW POWER. I BROUGHT IT BACK TO THEM. AFTER TESTING IT FOR THE SECOND TIME, THEY SAID THAT COPPER CUPS WERE THE PROBLEM AND SUGGESTED ME TO TAKE IT BACK TO THE DEALER WHO FIXED THEM. I FOLLOWED THEIR ADVICE AND FOR THE SECOND TIME TOOK IT BACK TO THE FIRST DEALER. HE FOUND LOW BOOST POWER, WHICH IS ALSO UNDER WARRANTY, BUT DID NOT GUARANTEE THE CORRECTION OF THE PROBLEM. LAST MONTH I SPEND MORE THAN $6,000 ON FIXING MY TRUCK, BUT THE SITUATION IS GETTING WORSE INSTEAD OF GETTING BETTER. SINCE I BOUGHT...