So I have a vop sop that is running a grid of points through an oscillation vop that is moving there position along the normal up and down. I want the speed of this to slow down over time and have keyframe animated a multiplier on the time in seconds. However, as it's animating there is a lot of popping as it slows. I guess because it is jumping to different points on the sine wave. I need it to slow down relatively quickly. Like there's a huge drag force on it. But want to avoid using a popsim.

Any suggestions?

If you want to control it with a multiplier POPs is the most straightforward, the jumping is caused by the fact that you are multiplying the total radians fed into the oscillate, really you should be multiplying the contribution at each timestep. If you're happy with an exponential slow down you can normalize your framerange, $FF/$FEND, then use a power function with an exponent less than 1 on it to slow down as you get toward the end of the frame range.