It's a turbo. It needs exhaust gas to spool the turbo. It takes rpm to achieve the required exhaust gases to spool the turbo. You have lag.
With the right turbo choices (I'm going to assume that for such a huge figure you must have one small and one bloody great turbo!) then you can reduce lag, and it will certainly be less noticeable on a large capacity engine, but it'll always be there. Without cheating via anti-lag, using an sc as well a la VW et al, it's mechanically impossible to build a turbo system with no lag. That said, I'd very interested in the details of your system, is there a thread on here or anything that contains all the details? As sad as it is, I love reading about engineering challenges of the turbo kind