That is what it was designed to do- upgrade PS1 and PS2 engines.
That said, when asking a technical question specifically about an engine, always best to give the MTH product number example 30-xxxx-x for a Railking and 20-xxxx-x for a Premier.
Diesel engines use a diesel upgrade kit.
Steam engines need the seam upgrade ki with the tether system.
Also note, upgrade kits are a bit hard to get right now. Not saying it's impossible, there are people who do upgrades and have tried to keep some stock of kits- many of them are forum sponsors.