Second image is a photo of my car, some of Josh's finest work which was his own words lol...
Straight after the modification you feel a big difference in throttle response and low end torque, they are both massively improved... it really transforms the car. The faster flowing gasses do cause the odd CEL to come on with exhaust codes as the lambdas get hotter now and think that there is something wrong with the cats, the solution is to buy a spacer kit and move the sensors out of the exhaust slightly, need to get round to sorting that myself... I am told that even the Larini sports cats will do this occasionally
No need for an ECU tune, I went on later to purchase a second hand Formula Dynamics ECM off the forum, sent it back to FD and explained the exhaust mods I have done and they took that into account when they reprogrammed it. In "peak BHP" mode it is quite beastly... revs freely, engine sounds louder and more pops and bangs from the exhaust... while in "economy" mode I have noticed a significant reduction in fuel usage on long haul journeys.
Also I have the incorrect clamps on mine the ones shown in the photo are for mild steel exhaust, I need to source the correct ones!