McConnell and Sobranie used coumarin (also a derivative of the tonka bean as is tonquin) but in considerable moderation and with more subtlety compared to most companies that use tonquin who can (as in 1792 Flake) lay it on pretty thick and it does ghost.
As Junkyard says, the tonquin ghost diminishes with smoking but I'm less patient and I'll give a pipe 3-4 bowls to clear the taste. Pipes that are reamed poorly (or previously so), where the integrity of the briar was breached (including scrapes (look like pressure marks), abrasions, nicks, heat checks and burns), can embed flavors. Same is true of shank and stem and for that reason I never use metal bristles anywhere in the pipe that has contacted smoke. Make sure that you clean the shank and stem but especially the mortise cavity and ream with a rounded edged blade.
I use a technique that I ONLY recommend to experienced smokers with heavily ghosted pipes;
If I smell heavy aromatics, tonquin or deer tongue in an estate pipe I ream, retort and smoke a little hot for the first bowl (controlled heat), less smoking and more bowl management. I retort the just smoked pipe (again) and feather any remaining cake and let the pipe rest for at least 3 days (more is better). You can use rum, whiskey or a mix of honey and potable alcohol to coat inside of the bowl as well after doing the above.
As noted, deer tongue can be a bear and you may note some offending aroma upon lighting but if it's not affecting the smoke then you're ok.
Hope that this helps.