Nothing beats a fitted seal, a snug proper fitting guide and a good quality spring.
Things like fitting an aluminum can as a sleeve in the piston or around the guide are not tunes, they are work arounds. I've recently received a few springers that had ARH Tar and what a fricken mess that was. Did it feel okay... yes, but it is not the best fix for the job. The amount of effort one puts into a springer from disassembling it and cleaning out all the factory lube, deburring, etc at least put a fitted guide or spring in.
What I recommend to EVERYBODY who wants a better guide/ spring fitment is to grab a caliper and once your gun is taken apart, then measure the diameter of your guide. For example, the Diana 430L. Has a guide that fits a Vortek 0.780" OD 0.118 Spring with 29-30 coils nearly perfectly. On the Vortek site there will be specs for springs including ID. Match up the specs to your guide, and if your gun doesn't have a tophat ask Tom to make you one, or someone else.
If you have a gun with a larger OD spring like 0.8-0.9" od, and 0.130 wire and it's super loose on the guide, you can go a step down on spring diameter and wire diameter to get the proper guide fitment. Assuming there are the same amount of active coils, and overall spring length. Two springs with the exact same wire diameter but different OD sizes will have different spring rates. The smaller diameter spring will have more lb/in. So I've gone down in diameter and wire size, made the spring 2-3 coils shorter added a tophat and had the same power. It was smoother as well.
Not a fan of factory springs from nearly any factory gun especially once it's had a couple tins through it with an improperly fitted guide and gets kinked. I also don't like to use drop in kits unless I have to.
Proper lube, sizing is very important. I've been asked what lubricant will last years with little to no maintenance in a springer. NO SUCH THING. I'm an idiot about springer maintenance, lubricant migrates gets in front of the seal etc. If you want to know your gun is in tip top shape I'd recommend a strip, inspection and relube at least once a year for maximum insurance.
Other than the trigger group, I strip my gun about 90% down for cleaning and relube, with inspection before every major shoot. That means I strip my tx on average of once a month during the shooting season. Things like my fun springers get stripped once a year or so to be cleaned up if they are used moderately.
Cam