2000 bonneville SE, w/ 2000 SSEI engine & tranny.
What have you done
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We can help to guide you on solutions to many problems or potential problems.
Begin conservative with the pulley size reduction until after you have opened up the intake with cool air and added headers and exhaust.
Start with a good modular system so you can go to progressive smaller pulleys to support each incremental upgrade.
Start with a 3.5 if nothing more than under hood uninsulated cone.