MiniBench was the problem I guess. I tried MacBench and enabling the cache quadrupled the CPU score. I'd still like to find the proper BCache control panel if I can. It also had some kind of compatibility setting where you could select 601, 603 and 604. Not sure what it did.

I'm using XLR8 MACh Speed Control now and I noticed that unlike the original BCache panel and the Powerlogix tools, the System Profiler displays the correct clock speed of 376Mhz. Before this it always showed 418Mhz.