Nissan Repair: 1993 nissan, e mail address, smooth as silk

Question
First of all I sent this e-mail and I think I keyed in my e-mail address wrong. Sorry!

I have a 1993 Maxima SE 91,xxx miles,VE30 DE 24 valve V6.
The front cylinder head back two lifters on the exhaust valves makes a lot of load tapping as if they are stuck.
Now heres where it get crazy. The first start up in the morning no noise for the first 3-4 miles, Then they start to tap after 3-4 more miles they stop. You can run the car on the hwy and run 65-75 smooth as silk,no tapping,Lots of power.20mpg city 28 mpg hwy. If you let the car sit for a few hours start it up and they tap right away and then may be not. ONLY the back two lifter do this no others. I have replaced with two new ones and much to my surprises no change. The inside of the head was supper clean no build up of any kind. I have run 2 oil changes in 200 miles with engine cleaner in them. Do you think the oil channel going to the back two lifter are some what  clogged ?? If so do you think it would be okay to remove the lifter and shoot high presser air down the channel?? I was thinking of using the AMSOIL engine cleaner and changing the car over to syntactic oil thinking might help. At this time I am open to any ideas. I hate to leave things like this go it has become a quest to figure it out.If for no other reason is to say I did. I can live with the noise but not at losing the battle. One of us will give up and its not going to be me.Your thought would be very helpful.

Answer
Dave,

You are on target, if the lash was set and it is within specification that would mean that the oil gallery feeding those lifters is intermittently plugging.  So, if you use AMSOIL or the like it might do the trick.  Now, if it does not that means removal of the head and chasing the galleries by hand to get them cleared.