It does indeed sound as though your spring is "tired". A new spring would undoubtedly pep your gun back up - it sure did my old Diana 34. A kit does not necessarily give you more power. What it does is give you a new spring guide which smooths things out and eliminates twang. Vortek provides kits with an external spring guide. I do not know if they have one with an internal guide which I prefer. I got my kit from Air Rifle Headquarters. I've not bothered to chronograph it but it has a LOT more power than the original spring. I think the Vortek kits come with a new piston seal while the ARH kits do not. I don't know what seal the Vortek will include as they have several offerings, some good some not so good. ARH only seems to have the one seal which is a lot like the original Diana seal. I do like that. Their seals tend to be tight so I do size them. I try to size my seals for 3 to 5 pounds of resistance on the lubed seal on the piston. Mark 611 likes about 2 pounds. Lower resistance will give higher velocities but will also allow the piston to slam into the compression tube with more energy. Like many things in life it's a trade off.