Formaldehyde will not get you high.
http://www.erowid.org/chemicals/pcp/pcp_info6.shtml

Formaldehyde is a known carcinogen linked to nasal and lung cancer, and with possible links to brain cancer and leukemia and should not be smoked.
I am also suspicious of 'LSD-laced' weed. LSD is very unstable and will degrade when just slightly heated let alone combusted.