The tungsten is great for the 700/800mm barrels. It's overkill for the 500 and 600mm barrels.
It will do two things. It will allow you be more efficient with your air with the medium/lighter weight slugs and will allow you to shoot the heavyweights without cranking your regs to extremes.
I've got it on my .22 M3 with power block and I prefer to shoot low to mid 30 grain slugs so that I can relax the regs and still get incredible performance. I've tweaked my reg down to 155 and I'm pushing 31.2grainers ~1025 fps like a laser beam.
I don't use the FX slug kit, I installed the NSA slug pin probe and it's been great. It's more robust than the FX probe.