Welcome aboard, Smitty. I'll move your post to its own thread in a minute (along with this response).
Turbo lag is unavoidable but marginally reduce-able.
The turbo only produces boost when there's enough exhaust pressure, and there's only enough exhaust pressure when the foot is down. There's always going to be a small amount of time between putting your foot down, the ECU responding to that and raising rail pressure/injector open duration and the exhaust flow getting the RPM up on the turbine.
Turbochargers have become smaller and lighter over the years to try and combat this - but you're asking a gas to overcome the inertia of a steel turbine and an alloy impeller on a shaft with oil-filled bearings. On our engines, decent boost probably isn't being seen until at least 30-40 thousand rpm on the turbo shaft - our turbos reach around the 100,000rpm mark at full boost. Going from near stopped to those sort of RPM takes time!
You can reduce the time by making sure ALL of the exhaust flow is going to the turbine - block the EGR tube. Now this has recently become a thing of concern, with one of our members here suffering an EGR blanking plate failure that, coupled with soot (which is dry partly burnt diesel) and mixed with raw unburnt diesel turned the EGR tube into a flame thrower that melted his EGR butterfly. The moral of the story is to use a blanking plate that is substantial enough - I'd say an absolute minimum of 1.2mm stainless sheet, and NEVER consider aluminium regardless of thickness because it melts at too low a temperature.
You'll find that your turbo won't be diverting exhaust through the EGR tube any more and all of it will be available to turn the turbocharger over - thus mildly decreasing turbo lag. Unfortunately, there's no way to EVER get rid of it entirely.
Even superchargers have lag - it's really, really minimal, but it's still there.