I have been spoiled with the blue foam mod on my 510's because it works so well.
However, on the 901's with their Whistle tip, I have been getting that icky taste sometimes, endless waiting for the juice to soak in, and the poly fill getting old very fast.
I tried pulling that poly out and using just blue foam but that was very drippy.
So, I took one of my used 901 whistle tip carts and with a pair of tiny cuticle scissors was able to snip out about a 1/4 inch (still experimenting as to how far to go) of the polyfill that comes in the 901 whistle tips. I added juice and the blue foam.
Tastes great, less filling!
Vape On!
However, on the 901's with their Whistle tip, I have been getting that icky taste sometimes, endless waiting for the juice to soak in, and the poly fill getting old very fast.

I tried pulling that poly out and using just blue foam but that was very drippy.
So, I took one of my used 901 whistle tip carts and with a pair of tiny cuticle scissors was able to snip out about a 1/4 inch (still experimenting as to how far to go) of the polyfill that comes in the 901 whistle tips. I added juice and the blue foam.
Tastes great, less filling!
Vape On!