Just my opinion... I did not have any tranny lagging issues or shuddering but still had it flashed. Nice! Waaaaayyy better. Firm as hell. Tight. Responsive, immediate shifting gear-to gear. Maybe a tenth or two tenths of a second lag (to short to time). Because of exhaust set-up I am in auto-stick 98% of the time and that is where the difference is really noticable, especially over 1800 RPM's. 2500+ RPM's very noticable. You can feel the difference in pressure shifting at any RPM. If you have not had the TCM flashed yet, do it! Again, just my opinion.