[Rodsrsr]

1 3/4" is way too large for a 3ltr or even a 3.2. The correct size is 1 5/8" and anything larger like Kach says, you will lose tons of low and mid range hp and torque. You need at least a 3.6 to run those large headers, so if the new headers are the larger size this is undoubtedly the problem.