I had a PO455 code ( large evap leak ) on my 99 Miata last month. Replaced the purge
valve near the canister. No more 455 code, BUT then codes 446, 171 and 1450 showed up !
Have done the research on possible cures. Have installed new Mazda OEM gas cap, cleaned
all canister ports into the intake mainfold and checked that all hoses near canister are clear.

No performance issues noticed other than low RPM during initial warm up period, maybe
5-10 mins. MIL is ON, have reset once .

What should be next ? Tank pressure sensor? Canister cut valve?(what is that and where? )
Haynes manual says carbon canister is under the car near tank, but mine is in the engine
compartment....maybe an early version of 99 NB.

99 Miata, vin last 6 digits 123254 , mileage 99,200