Having worked in an engineering environment my whole career the need to improve or optimize everything is strong.
Used to be that finding the best pellet satisfied that need but since realizing the the generic factory tune could really be improved on I've become a serious tuner.
I have some fine PCPs (Air Arms, Daystate, Weihrauch, Walther) that are not (easily, without disassembly) tunable, they shoot well enough as received but the groups are not as good as the airguns that I can fine adjust. I'm not selling them, they are great for off hand plinking and such but for serious work like hunting or target shooting I use rifles I've custom tuned to a specific pellet/slug.
These days I won't consider buying a PCP that doesn't have (reasonably) easy access to the regulator and hammer spring adjustments. Once tuned, I'll leave well enough alone unless I decide to use a different projectile.
I don't mind doing minor mods (like deburring, shimming and polishing) and I won't hesitate to rasp a stock to make it fit properly but I'm not into "hot-rodding" an airgun to increase its power. 30-33 fpe is plenty for my needs.
Cheers!