Sunlight, heat, water, and fertilizer should give you fast growth at this time of the year. Do you know which passi that you are growing? They are not all the same.

I do all of that and it has still slowed. I don't know the name, it has purple/pink flowers though. It does not bear fruit yet.

How big is the container? It could be rootbound now (they fill up pots real fast)!

Doesn't being root bound cause the plant to become top heavy, hence growing rapidly and filling up now that the energy isn't put into root growth?

Well, I will repot it soon, I checked and the roots are coming out of the bottom. Same thing with my clematis- but I know those don't like containers. But I had to have it!! I will let you know. Ginger's comment did spark some interest in me though, it is a relatively young plant.
Thanks

There is a limit to any top growth once the plant is rootbound. What often happens, aside from the container now drying out much quicker, is that it either slows or some of the side-shoots will start to wither away.

BTW lighter - I've had a clematis in a 21" container for going on 5 years now. ;-) In that case, because it's a group 3 (blooms on new growth only), it gets wacked back every late-February and thus the root system easily supports the massive growth that it does each spring. This is something that one wouldn't do to group 1s and would do selectively on group 2s. This is a bit different than the passi - although those could get wacked back too and should resprout.