Injector Pump Timing + Fuel Screw

Hey guys, I did a bunch of searching around but I couldn't find an answer to this exactly. Feel free to smack me over the back of the head and show me if you know of a thread though.

I have an original '89 NA silvertop TD42 with an aftermarket turbo on it (I think it's a Switzer S2A). I had a pretty bad injector pump leak that I asked about a while ago. I've gone and gotten a reco 10mm pump from a mob down near Wollongong. When I installed it I set it to the factory timing for the NA specs (.74 at TDC), but i'm finding the the turbo to be really laggy, and it basically won't push out any boost unless it's revving pretty hard. I was wondering if I retard the timing a bit, say to maybe .70, would it make the turbo spool up sooner? Or should I be heading straight for the fuel load screw?

Regards,
Christian.