I posted a few weeks ago about how I had changed from the N75J I was using for the standard item, the N75C, and was very happy with the results. Now, I like to follow these things up if at all possible.... so that's what I've tried to do. Thanks to Bill @ Badger5 for the use of the dyno for this testing.... :thumbsup: I have dyno print outs of both runs below. The comparison in the boost curve between the two valves is incredibly different. Anyway.... J Valve The J valve is very spiky as we all know. Gives good initial boost - around 20-21 psi on my setup @ around 4000 rpm, which then fades away very sharply to around 14 psi by 6000 rpm. Based on this, the torque delivery suffers badly after the initial spike, dropping like a stone through the rev band. This will be seen on the dyno print I will post later. So really, the J valve is a trade off. Peak PSI is increased earlier, but to the detriment of the later stages. The turbo gives it's all early, and runs out of puff much sooner. Not good IMO as really affects driveability of the car when on the road. This is due to the torque curve following the boost curve the sooner the boost dies, the sooner the torque dies. On another note, I have also found that long term fuel trims were more out when on this valve.... But may just be my motor. Graph here: Sadly, there isn't a breakdown of this one as there is below, however it does show Flywheel power, Wheel power, torque and boost. Note that boost is down to ~16 psi by 6000 rpm. C Valve Mine is original and old.... lol. Noticed an immediate difference in the power delivery when using this valve. Boost is less spiky, and comes on in a much more progressive form. Peak boost is less, however holds that peak boost for a much longer period. As can be seen from the graph below, the C valve doesnt actually achieve peak boost until much later in the band. Sustainable boost is held from ~3600 all the way to 6000 and beyond. Torque when using the C valve is reasonably stable through the same band. IMO much better. Graphs here: Boost hold much better, and peak torque when compared to the J valve (225 lb/ft) is much higher. MBC Will add this when I have fitted it and had it re-run.