mustang_gt_guy

I have a 2000 mustang Gt with 4.6 SOC, with a slight rattle noise in number one cylinder. Noise goes away when I unplug injector in that cylinder. I switched out the injector with another one and still have the same noise in same cylinder. I also swithched out plug and coil and still same thing in same cylinder. Compression test shows fine. The noise sounds like what a older model sounds like with a loose valve, but the noise only happens when engine is at around 2000rpm and mostly just under light throtle and as the engine rpm's increase so does the noise but at idle or even reving the engine the noise is not noticable. Under a heavy load 5th gear the noise is not heard but mostly in 1 through 3rd gear with light throtle Just before i noticed this noise starting my car kinda acted liked it dieseld wile taking of from a steep hill, its a standard and the engine almost died then acted like maybe it dedinated alittle but never died or anything, i just wasnt giving it enough gas wile taking off. If you have any input on what you might think it could be please feel free to through it out there.

mustang_gt_guy

Please post any ideas please! P.S, i took of the valve cover and no ovious sign of damage. Totally stumped on what this odd noise is do to the fact i can only hear it wile driving it and not wile its idiling or by reving it up.