Stains on intake plenum and other engine parts Got a fix??

Not sure, they don't really look clean to me. Have you tried any degreaser like simple green or 409 and a soft/medium brush?

 

Use Groits Engine dressing spray (you may have to order it over the internet). It will make the spots disappear until you clean it again. Over time, it may help "lift" the stains. It will make it look MUCH better and has a satin shine to it. It does not collect dirt - good stuff, as I use it on my 360.

 

Mother's Back to Black and their deep trim cleaner may help. In all, you need to remove the stained and oxidized layers of plastic on top and get back to the even pigment underneath. Maybe try wet sanding with 1000 grit and then rubbing compound? Or maybe the blue-green shower scrubbies safe for fiberglass and enamel? Either way, you need a fine abrasive (deep trim clean with wire brush) and a polish and restorer treatment like back to black and the plastic dressings. 348's are wrinkle painted and I wonder about changing my color - no sanding. Also thinking or chrome plastic intake hoses for more growl, heat reflection (minimal), and bling.

 

Like John K has suggested, wet sanding but I would start with something milder like 2500 or 2000. Another item that does a good job is 0000 steel wool. That may sound harsh but it works on mildly rusted chrome and does not scratch. Both of these approaches followed by a plastic polish mite bring them back. After you get to this point any of the products already mentioned should seal them going forward. Whatever you do, just try a very small area to see how it goes. Good luck.

 

Yeah, pick a far corner and try a bit. This is how the headlight restore kits work.

 

For the plastic, try Novus plastic polish (Novus 3 for heavy deposits/scratches, Novus 2 to finish up).

Then look at the various semi-permanent trim coatings to seal the plastic and bring it back to a new look. Haven't used it yet, but I'm intending to try CarPro DLux on my 348's faded interior air intake in the front hood: CarPro Cquartz Dlux - In Stock, Tested & Reviewed - Auto Geek Online Auto Detailing Forum On sale: http://www.detailedimage.com/CarPro-M53/DLUX-Plastic-and-Wheel-Coating-P940/30-ml-S1/

For aluminum you're probably looking at media or vapor blasting.

 

Yes milder is better. Once you get in to an even finish, the stains should be gone and the pigment returned to an even color. The dressings will seal and make this pop. Plastic polish may be even better. Use it on the Spider top window.