By the way, adding a tighter spring or adding a restriction to the reference line (which I didn't discuss) won't fix the problem... they're hacks which will cause another type of problem and just REDUCE the existing one... you'll still spike rich when shifting (which has NOTHING to do with how rich the car runs normally) and you may still run stall periodically. They're just hacks.
With a healthy turbo a LITTLE surge isn't a huge concern and will improve throttle response during a fast, high load shift (see automatic transmission
)... It's not something you want to expose an old turbo to as much as possible.