Physical Stuff
Besides an installation instruction page, the kit comes with an entirely new valve system with a volume chamber and attached vertical ASA adapter, new hammer (a.k.a. rear bolt), new main spring, rear cocking mechanism, side cocking slot cover, a braided steel air hose with a quick disconnect and a small tube of lock-tite.  The hammer is the most obviously changed piece of the gun, looking like a chunk of swiss cheese because of the number of large holes drilled through it, and weighing noticeably less than the stock piece. The main spring is larger in diameter, resembling those found in a Spyder. The rear cocking piece connects the hammer, main spring and replacement end cap.

Installation
Installation of the kit is fairly straightforward on paper, however, there were a couple of minor complications encountered as I re-assembled the gun. First off, the small grommets which help hold the cocking slot cover interfere with the travel of the hammer. With the grommets in place, the hammer does not move smoothly enough to function properly. The easiest way to address this problem was to leave the cover off. The second (and related) problem also involved the movement of the hammer. With the body halves of the gun bolted together, the hammer movement was still somewhat restricted, as if the diameter of the hammer was too big for the internal diameter of the gun. I used a small washer in between the body halves, on the rear frame screw just below the cocking slot. That solved the problem and allowed the hammer to move freely. It should be noted that we have encountered similar problems on three different Model 98s (1 standard and 2 Customs) on which the kits were installed.

Performance
As in any low pressure operation, this kit requires the addition of a regulator, whether on the gun or on the tank itself. Although the kit was designed for the purpose of making better use of HPA, it works fine with Co2, which is what I have been using. Upon charging the gun up, the first thing I noticed was an incredible increase in velocity. I have not put a gauge to the system, but have little doubt of Tippmann's claim that the system allows operation in the 300 to 400 psi range. With my current set-up using a Palmer Stabilizer regulator, the adjustment is backed nearly to the bottom, indicating a low operating pressure. I suppose I could yank a gauge off another gun and stick it on the Model 98, but actual operating pressure is actually irrelevant - what counts is the performance of the gun.

A rather large volume chamber attached to the valve protrudes from the bottom of the gun.Using the kit does require a regulator which can flow a large volume of gas at a low pressure. A restrictive regulator will result in "shoot-down" over a rapid string of shots.   From a standpoint of operating, since the installation of the kit and a good flowing regulator, the gun has not failed to re-cock - not once. In that respect the kit has not adversely impacted reliability, which is a common problem in low pressure conversions. If anything, from my observations, the ability to re-cock has been improved. It is also a noticeably smoother process. With a lighter hammer, there is less felt "recoil" in the operation of the gun. The gun is also quieter.

As far as the performance of balls out of the barrel, the gun seems to hold much more consistent velocities. A chart on the stock gun performance over a 10 shot string can be found on the entry-level gun comparison page, indicating jumps of as much as 10 feet per second between shots and a 20 foot per second spread over the string. With the current set-up, the gun has about a 3 foot per second variance with a rare occasional drop outside of that range. Of course part of that consistency comes from using a regulator, however, I have tried regulators on the stock gun, and the impact was minimal. Working with a lower pressure apparently puts the regulator to work, making it more effective.

Opinion
The gun makes less noise, kicks less, and holds more consistent velocities with use of the kit. As is the case with most LP modifications, overall operation simply feels smoother. The one disadvantage is that the gun seems to be a bit more of a gas hog than it was in stock configuration. I like having the kit on the gun, and the advantages it offers, especially the consistency, which was a major problem I had with the stock Model 98.  Is the kit a "must have" for Model 98 owners? No, the stock Model 98 will work fine for most people. What the kit does is offer some improvements for those who have the money to spend and like to tinker with performance. Anyone considering the kit should keep in mind that the $120 price tag does not include a regulator.