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Both Lingenfelter and Hennessey(not an endorsement) offer add-ons, I'm sure others do too... have you checked with the forum supporting vendors? Callaway also comes to mind as a possible source.
U want more power for that ZR-1 get headers. Long tubes and a tune with cols air intake. Probably gain another 50 rwhp. For a car like that I would take it to LG or someone that has alot of reputation.