I'm slowly figuring out the ins and outs of DIY and all of the flavors but coffee remains a mystery to me. I'm using TFA coffee flavor and I made few batches anywhere from 3% to 12% letting them steep for 3 weeks although I tried the batches in the mean time. none of them taste like coffee and I know my coffee At 3% there is absolutely no flavor, at 8% I can almost smell it, at 12% I'm not sure what it is but it's not coffee. All I want is a simple coffee liquid, straight up without anything added. What am I doing wrong? Should I go higher? 15%? 20%?