Here's a quick little review of a product I've just bought and installed, the Super Light Pump Stroke (SLPS) Cocker Pump Spring Kit, available on eBay from a seller called "apes4all," or on MCB from a user named "maggot." For $12 (on MCB) or $14 (on eBay) you get two springs, in a padded shipping envelope. Shipping was quick. I Paypaled the seller on the evening of the 13th, and received my springs today, the 18th, in the mail. No installation instructions come with the springs, but it's pretty straightforward if you have an autococker valve tool and a set of standard allen keys. All you do is remove your lower internals, switch in the new valve and hammer springs, and re-assemble your marker. Then you just need to re-chrono, to get your marker shooting at whatever field speed you want. I spent more time than I should have installing the new springs into my 05 Prostock pump, just because I managed to get the valve twisted, so initially I was shooting about 2 feet per second because the exhaust hole on the valve didn't line up with the air passage between the lower and upper tubes. I took everything out, reinstalled it more carefully, and was good to go.
Yes, you're paying $12 for a couple springs that probably cost the seller less than $1, but he did the legwork to figure out what combination of springs work well together, so I don't really have a problem sending him some cash. The good news here is that the new springs did make my pump stroke significantly lighter, and I was able to get my velocity back up to 300 FPS easily. Some people who've bought this kit have reported being able to pump their markers with one hand without touching the pump handle. I'm not quite there, but suffice it to say that very little effort is now needed to cock the marker, and auto-triggering is much easier and smoother. I'm happy with the purchase.
I have no affiliation with the seller, other than having bought his product. Hope this helps someone.