You should be fine popping all 8, but only if it's been 24 hours since you took those 6. If not, I would wait at least 24 hours. The daily max for acetaminophen is 4,000mg. You don't want to fuck your liver for what sounds like won't ne much of a high.
Lol, I was down to 20mg of methadone, down form 120mg, coming off 2-3 grams a day of h/fent. I didn't feel shit from the h that's how high my tolerance was. I was on the 20mg of methadone for probably 2-3 months. I ended up taking 5 10mg oxycodone and actually got high. That lasted 2-3 days. Back on h/fent. Point is, it was cool to feel that high again. Now I'm back at 1-2g a day of just maintenance. Never should have taken the pills again. Started with drinking with a work colleague. Fuckin booze.