top end tick and rough high idle

[SpoolingNation818]

I am new to Nico and i recently bought a 90 240sx. the car has a twin cam ka24de and when driving the motor tends to have a repetative tick coming from the top end. this only happens when driving the car. at idle it does not tick. i've been researching it and came up with a few things that could be wrong... Valve seals are bad, timing chain guide or possibly a bad lifter? the tick doesn't change tone at all it's just a constant tick tick tick. im just curious if anyone else has had this problem before also

another thing is my idle is very rough. when i start the car it revs up a little past 2k then slowly comes down to around 1400-1500 and after a few minutes it reaches 1100. sometimes it acts like it wants to die and bounces from 500 to 1000, it has actually died a few times from this. when driving the car and coming to a stop i push the clutch in and the idle almost goes all the way back to 2.2k or so then when fully stopped it crawls back down to around 1k. could it be my tps? any info is much appreciated. thanks