Originally Posted by gernby

The OEM design is a standard Tri-Y with a better configuration. The thing that I believe is bad about designs like this one (and Hytech's) is that they are pairing cylinders 3 and 4 together and 1 and 2 together. By doing this, the pulse from cylinder 3 at the secondary merge collector will cause scavenging on cylinder 3 and 4. However, the pulse from cylinder 4 will only cause scavenging on itself. The same will happen with the pulse from cylinder 2, so cylinder 1 will also get 2 scavenging pulses. So at the engine RPM where scavenging is at its peak, cylinders 1 and 4 are going to run significantly different than 2 and 3. Ignition timing and fuel would really need to be independently tuned for peak performance and reliability, but I don't think any EMS allows separate maps for 2 cylinders. If you just try to use individual cylinder trims to add a few percent more fuel and retard timing a couple degrees on cylinders 1 and 4, that would be safer, but you would be loosing performance at the lower RPMs where 1 and 4 aren't getting double scavenging.