If one would want to make amphetamine (not meth) out of P2P, which would be the reaction with the most yield? (And could one maybe link me to this one)
I have had bad luck at trying to find a synthesis online, but the one I found (Al/Hg with ammonia) specifies a 30% yield,
and the leuckart doesn't specify a yield at all. The other synthesis all specify P2NP, but I'm looking for the P2P synthesis.

With ammonium (acetate) it's fun for MDA manufacture...

Dissolve the ammonia salt in ethanol (methanol preferably), add a stoichiometric equivalent of KOH in one dump. Stir the mixture till it dissolves and then add in your dissolved (in alcohol) ketone slowly (dropwise) over about half an hour, stirring is continued at room temperature for another 30 mins. Then, slowly add in a reducing agent, preferrably a weaker one like NaBH4 or NaCNBH3. !Organic Syntheses, Coll. Vol. 6, p.499 (1988); Vol. 52, p.124 (1972). Perhaps you should look into reductive amination with NaBH4...

hXXp://www.wetdreams.ws/forum/mainuploadsfolder/C_C_C/20061123135746_Amphetamine_sulphate_synthesis.pdf

What about the leuckart with ammonium fomate or formamide withp2p, you heat it for a few hours at 160-180°C under reflux and then either hydrolyze the N-formyl-amphetamine, or reduce it to yield methamphetamine.

As said above check rhodium, there's plentiful of information about this subject over there.