[Kyle Sowden]"I have a .mov clip of spinning text, I added particular to an adjustment layer above it so I could create a look kinda of like the particles are being dragged into the centre of the spinning text."
You do not need to apply Particular to an adjustment layer. Apply it to a solid and it'll work just the same, only more predictable.
Also, you cannot time reverse a particular layer unless you pre-compose (with "Move Attributes..." selected) that layer.
Particular does have a built-in ability to play with time though. It's called the Physics Time Factor and it's located in the Physics section. The default value is 1.0. If you increase that to 2.0 you will have twice as many particles emitted per second moving twice as fast per second. If you animate it to 0.0 then you will freeze any particles that have already been emitted. If you set it to 0.0 from the beginning then no particles will emit (because time is frozen and the particle emit rate is a function of time).
If you want 5 seconds of particles flowing inward, you can set a PTF (physics time factor) hold keyframe at frame 0 with the default 1.0 value, then move forward 5 seconds and set a keyframe with a -1.0 value.
Then trim your layer at the 5 second mark, where the -1.0 keyframe is, and move the new in point of your layer to the beginning of your animation.
You have to have a positive PTF before you go negative because otherwise there will be no particles emitted, it'd be like trying to rewind a tape (i'm old school like that) when you're already at the beginning.