I would try a step or two lighter springs on the metering rods. If it gets better, you're "going the right way". BUT, there may not be enough "room" with just spring changes. You may need to run bigger metering rods. May even need to re-jet it. Between springs, rods and jets, I don't think there's any doubt you can get it done.
I do think that an A/F meter will help you greatly in this instance. Worthwhile investment for sure.
I have to agree my wideband O2 sensor was not only extremely easy to install but helps tremendously with carburetor tuning. Seeing as how I run two carburetors at once it becomes even more tricky... LOL
I think back when I ordered mine they wanted $209 at Summit that they price match for like just under a hundred and fifty bucks for everything..
This is perfect timing to install one because I’m about to make a custom gauge cluster with some new gauges. I’ll have to work an AFR in there somewhere. I had one on one of the miatas I had and it was essential in not exploding lol.