Hi folks I have a question about ignition timing on a Celica vvti on 70hp jets.

I will soon be up-grading my install from single port to direct port and hope to gradually increase the jet sizes from the current 40hp jets up to 70hp. My question is since the Celica has variable valve timing does this mean that I shouldn't need to retard the timing when moving past the 50hp jet range as the engine automatically changes its timing anyway?
You are confusing CAM timing with IGNITION timing, when adding larger quantities of nitrous you need to retard THE TIMING - NOT the CAM timing.
50 to 70 HP is border line for needing to retard the IGNITION timing, so it would be safer to retard it but you may get away without doing so.
Having a progressive controller means the need to retard the timing is less of a concern.

Once I install the final up-grades to my install (hopefully this weekend) it will be direct port, bottle heated and minimaxed. I dont know much about altering the timing of this engine so just need to know if I can run 70hp jets without retarding the timing.
It's unlikely that you'll actually be able to retard it, so use soft Minimax settings and it should be fine.