When it comes to APAP, from my own experience, there is no need to have any amount in your system when you are using opiates, and even so going over 1000mg is not really recommended, try taking 1g of APAP on its own, and see how it effects your body. It may not impair your liver but as a general practice, I would always do CWE, there is no need to expose your liver to APAP at 2g or 3g in a day for no good reason. Sure, people could take even 5g and not end up with any APAP poisoning but I just do not understand what purpose does it serve when there is a very easy method to remove the chemical from your final solution. People really need to pay more attention to each substance being put into their body, regardless, if it is considered a safe-level. Do not take the ingesting of substances into your body lightly, don't forget they have effects on the way you experience opiates.