First, any and all help is greatly appreciated. I feel its very necessary to give a brief history on my 2005 Nissan Maxima 130xxx mi. love.

Transmission give me no problems. Most recent self-fix was a camshaft sensor 4 months ago, and has been running great ever since. Most recent issue I'm posting for is a rattling noise on the passenger side which I believed I've doctored down to the intake manifold. (not 100%) Scares me only because I have to make long drives if any. Occurs around 2200 RPM, once starting up and when accelerating. Also feels this might be causing a slight/occasional power loss on acceleration

Ive been making a long mistake of using regular gas as long as I can remember. I now want that change to prem. to happen. Other than that a VERY recent high pitched squeak is coming from the inside, going over any and all bumps.

If possible can I get some other possible causes of rattling in that immediate area, if I should use an injector cleaner, and anything else I need to be on-top of before I make ANY more trips. If needed I've found several youtube vids with identical diagnosis/sound.

Again any and all help is very appreciated.

 

The rattle could be your tensioners shoes going out, very common/ could be a heat shield on the y pipe also very common. You can use injector cleaner, I may need some myself.... Check for oil leaks around the valve covers if you have some change the valve cover gaskets. The squeaks are more than likely you strut mounts, are you still on stock shocks and struts?