That hasn't been my experience. I went from 18 mg freebase to 18 mg nicsalts and noticed little difference other than smoother taste and lack of harshness.
I was under the impression that nic salts are more quickly bioavailable than regular nicotine but I was recently informed that in fact, freebase absorbs more quickly than (many not all) nic salts. So, I'd guess you may be feeling a "lag" in effect, possibly, and also perhaps the lack of nic throat hit is "fooling" your body into thinking you aren't "receiving" nicotine. IDK. I finished my stockpiling with freebase nic, and now that my throat has recovered, it will be an interesting experience to see what's different (it's going to be a while, I just opened a liter of 100 mg/ml nic salts.
The only other thing I could have seen as possible is that you didn't enter a variable correctly in the juice calculator and it's possible your mix is lower strength than you think.
You could try a higher level of nic salts if you want. You could also try a mix that is half nic salts, and half freebase, and see what kind of results you get.
The only thing I know for sure is nic salts are slightly different in smell and flavor, and lack pretty much any throat hit which is why they can be mixed and sold at such high levels. I didn't notice much difference other than that. It will be interesting to see what differences I note when DIY with regular nic, instead and etc.
Anna