I thought the booster pump you are now using is meant for 2-300 ROMan systems not 4040???
I use a full 1000 litre tank, 1&1/4inch tubing to push a high volume of water through my 4040 using a clarke booster pump (140 lpm), with waste set to high to keep my TDS down to a minimum and polish off through 2 DI containers into a 2000 litre storage tank ready to transfer into van whenever needed.
4040 low pressure RO works best when using highest pressure under 225 psi.
I've found hot water goes through the R/O much quicker than cold water. My water before RO gets heated from being stored in a tank left basking in the sun (when it's out) from sunrise 'til 4pm.