misomeru

I have a 5 speed sc300 with 124k miles. doing its first tune up since I purchased it. I am confused on what spark plugs to get for it. I'm sticking with denso as far as I know. I love to keep everything running like original with original parts. I see that the 1992-1993 use the PK20R11 Denso plugs but from 1994-1997 Lexus lists using PK16R11 Denso's. Why is that? I have ordered cap, rotor, pvc grommet, 3 intake related gaskets, fuel filter, oil pan crush washer, cord set, plugs, air intake, oil filter, coil assembly, distributor o-ring related refresh items and some misc grommets for oil cap and something else I cant remember. Later I plan on doing t-belt/water pump and related seals when I get more money. It seems like I may have a head gasket leak since my coolant keeps needing extra but I just did a radiator flush and drove with plain water for a day and flushed it a total of three or four times till water came out clean! Replaced coolant with toyota red 50-65 percent water to coolant since it still offers -31 to -35 whatever it was protection. I used measuring tool dropper to verify. I may try and get a new radiator cap to see if it helps somehow with missing fluid in coolant rez tank, also since everything is stock and probably hasnt been replaced. This car was not driven much so now it needs a lot of attention I understand. I do also notice that when I start the car i hear a loud cylinder or more be extra loud or it could be valves needs adjustment? Car passed Texas state inspection after coolant flush, new oil and filter, cheveron techron injector cleaner, a new fuel pump and filter and a full tank of premium and a 100 mile drive. Cant wait till my parts get here.