normal driving every thing is fine---hard accelaration rattle sounds on right front--95% of the time at exactly 3500 rpm up to 3800 rpm---could it be timing chain/tensioner/ guides dont know if take to dealer or try changing tensioner?

 

its possible its timing chain related but I doubt it.

the engine could be pinging- what kind of gas do you use? octane? quality?

 

I have the same problem with my maxima. After getting the timing housing gasket replaced it starting making the rattle on hard acceleration. The place I got it fixed at tried to tell me it was pinging but I always fill my car with premium only and just changed the knock sensor. Another quick diagnosis I got was a problem with a tensioner. I think the shop messed it up when the took apart my engine for the gasket-- I do plan on taking it to the dealer to find out exactly what's wrong...

 

I kinda doubt it's pinging.

 

loose header?