i found the spacers added about 15-18 hp in my midrange, tuned with headers. Top end did not change, but I have not SSIM'd or removed the vias. YET. ssim is sitting on my basement floor waiting for the warmer weather.

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6MT | 06HLSD | I/H/E & FC | Stillen FSTB & RSB | Eibach Pro Kit | Illuminas | Watkins STS | UDP | NWP Spacers | Greddy Blue | ES Bushings
253.50 fwhp
249.75 lb/ft tq

14.3 @ 101mph (street tires, bad wheel bearing and a few spun tranny bearings)