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In my opinion....Stock ECU unless you have aggressive cams (definitely must be above stage 1 cams) or forced induction.
Header, intake and 2.5" mandrel bent exhaust will get you around 25hp to the crank.....so 18-20whp gain for $500-1100 (depending on brands and if they're new or used). Or (at least) triple that amount and run turbo to get 200-225whp total and have a fun handful to drive.
A chip and dyno tune will add more if you have those bolt ons. How much more after bolt ons? 10-25whp is my guess. You could get close to 150whp with bolt ons, socketed ECU and dyno tune. Socketed/chipped ECU and dyno tune....probably $500-600.