Next time read the drug facts, look for a bottle with DXM HBr as the only active ingredient. There are plenty of brands with DXM as the only active ingredient and they aren't hard to find.
Yes, you can still consume the formulas with the guaff in it, but it's really not recommended and I'm sure is only going to cause negative side effects down the road with repeated use. That is IT though, anything else in the syrup and you wasted your money. You don't want any APAP or any other shit. Then you're just asking for trouble.
And honestly, DXM is such a shit high. Terrible dissociative. I'm not here to push other dissociatives on you, but I'll definitely urge you to stop messing with DXM. There's a reason it's legally sold over the counter, it's garbage.
And downing a bottle of robitussin.... the thought makes me want to vomit.
Better yet, order yourself some DXM in powder form so you don't have to deal with all the syrup bullshit and searching the pharmacy for 20 minutes.