Hi I have a 2008 Lexus ISF with 200k on it, I bought the car as a 2nd owner it had 40k when I bought it, now it has 200k, I've done all the recalls and done the regular oil changes every 5k and replaced the transmission and diff fluid at 75k.  Replaced majority of the suspension with performance for just handling.  Other than that the engine, transmission, exhaust is 100% stock untouched.
Recently I took the car in to get the knock sensors replaces, due to it was giving me a knock sensor code, and misfire on cylinder 8, I brought the car in to my trusted shop they replaced the 4 knock sensors and re-done the sealant that was causing me the dreaded valley plate leak for the ISF's engine (2ur), but I still have a bit of a rough idle.

I have already replaced the following:

coil packs, spark plugs, battery, valve cover gaskets and spark plug seal tubes, port injector on #8 (reason being when I inspected the spark plugs it had oil in 8,6,4) vacuum line, PCV valve and hose.

NOW
I have the following codes: p0201 (injector circuit/open cylinder 1); p0308 cylinder 8 misfire detected; p0301 cylinder 1 misfire detected; p0300 Random/multiple cylinder Misfire detected.

Basically what I have done was in this order:
1) replaced coilpacks and spark plugs and battery
2) brought it to a shop replaced the knock sensors and re-sealed the valley plate
3) replaced valve cover gasket and spark plug seal tubes
4) tried to clean the valves with the STP-PRO series intake valve cleaner
5) replaced PCV and hose.