You are one of the few who pick up the chemical taste of pg. I do also. DOW is the only one I could tolerate. Tractor supply, TPA's tastes terrible to me.
Wow, I thought I was the only one! I can taste a chemically, almost copperish taste with PG. I can even smell PG. It smells like chemicals, almost like gasoline that has been heavily diluted. And yes! I love TFA's flavorings but I completely stopped using TFA PG(their's is the only one I have). I just depend on my PG content coming from my flavorings and nicotine. Which works out considering I like high VG. Then I do 5% distilled water. It ends up being the viscosity of 70% PG while being 50 to 80% VG. I find the water almost smooths the taste out. I get more a water after taste than a pg taste. I find I love the taste of VG, though.