95% is abosrbed instantly, thats a fact. So, for the 5% go for it, but i doubt it'll make much differnce.

you shouldnt hold a hit in, 3 seconds is roughly a natural breath, and that is long enough. No need to hold it in for any longer than that, it doesnt do anything, if you DO feel anything it's placebo and nothing else, either that or oxygen deprevation.

All holding a hit does it coat your lungs in tar, and make you cough, for what reason? For NO reason.