Reducing power

This isn't something I ever thought I would be asking but guess theirs a first time for everything.

I own a Supra with a fully built 2JZ-GTE and my wastegate spring pressure is at 1 bar. Unfortunately its producing far too much power at only 1 bar than I originally thought it would. It's running a 6870 turbo and runs over 1,000rwhp on high boost but I would have thought 1 bar of boost would produce fairly low power (500-600HP).

This prevents me from enjoying the car on traction limited roads as the power comes on very hard, feels like 700HP minimum. I played around with traction control but now looking at other options to reduce power at only 1 bar.

I am thinking of reducing timing for just the 1 bar row, does anyone foresee any issues running far less than optimal ignition timing on purpose?

Exhaust gas temps could be problematic. With a turbo that big you could get away with adding a 3 port solenoid in the ref line to a BOV if you have one fitted with active ref line back to the turbo intake so the BOV opens when you power the solenoid and you are on boost, this should limit you to around the BOV seat pressure which I imagine would be around half a bar? Turbo that size and at that low pressure is unlikely to go near max speed even with the relief.