I'll play devils advocate here for a minute. I just bought a set for my 340, they are replacing the 7mm Accel yellow superstock wires that were on it. It is a night/day difference on aesthetics and fit/finish. I dont know about performance forsure yet, but there is something to be said for the quality of materials, look and fit these wires have. Plus I like the fact that they are black. I just dont like the "aftermarket" look of yellow or blue wires. In my opinion they are subtle, yet make your engine compartment look much better and are very nice. Are they worth the $129 price tag? that's up to the individual...
Once I get my motor back together I'll post a performance review if I notice anything. Since I'm replacing heads/intake/carb it may be difficult to narrow it down to what the wires alone did for me. I suppose I could swap back the Accels for a test though. We'll see...