The portals inside of TPT right now are very basic - you just take whatever touches portal IN, and teleport it into portal OUT. That could be enough, but, for instance, if you have a fan right at the exit of portal OUT, particles near portal IN would not get sucked in, since pressure isn't teleported. Same problem with gravity. Yes, teleporting pressure and gravity would lag more, but that's why adding a switch into the settings of the game would be the best solution(Just like with water equalisation). There's also a possibility of making it so that portals behave like real ones, being able to transfer stuff both ways, but I'm pretty sure that has already been suggested and would be a lot harder to make. The solution for at least pressure, would be to take the pressure value from near the portal IN, and copy it to portal OUT. I don't know much about how gravity works, so I don't want to make inaccurate claims of how to make it.

Okay, I found out how gravity works in here, and it turns out it would be just as easy as implementing the pressure teleportation. You just take the GY and GX value of where the Portal IN is, and copy it over to the Portal OUT on the same tmp channel. Teleporting back and forth would be trickier, but still possible. If, for example, a particle is in a 7 pixel radius, you check it's velocity. if on the next frame it will be inside of the portal/will go through it (since the portal shouldn't be a solid), you copy it, and on the next frame you delete the original, pasting the copy right next to the other portal of the same channel, opposite to the side of where it was supposed to enter the first portal. 

@Tadpole1 (View Post)

 That's a good idea too