As you can clearly see from the picture to the left, the pack had some major overhauls done to it. Most noticeable is the large green tank attached the left side of the pack. This is the packs slime blower attachment, essentially infusing the pack and slime blower into one ghostbusting piece of equipment.
The pack has additional tubing running from the beam line tubes up to the HGA, running to the ion arm and in cases using alligator grips to bodge the connection. The gearbox has a heat warning light and vent, the crank knob is completely missing. The ion arm sports 2 ion arm rods now and an addition power cell box is situated next to the sync gen at the right side of the pack.
The thrower too has had a major overhaul, doubling in width. Notice the separate slime tubing that runs alongside the loom into the new plasm distribution system on the thrower.
A large cylindrical drum wraps around the the middle of the gun with glass valves protruding from the sides. On the front, a slime blower cone runs alongside the standard thrower barrel.
A detailed overview of the changes from movie pack to video game pack can be found here.
The 4 iterations of the pack as seen in the game. A new lot of equipment is added each time the pack is upgraded. Starting left, standard proton pack, stasis stream upgrade, slime blower upgrade and meson collider upgrade. Notice that the two ion arm rods move upwards and separate on the meson collider.