Cleaning 5.0 Intake runners

I have a few 88-93 5.0l intakes, that I would like to clean up before I sell them.
Since there isn't much money coming from the sales of these intakes thanks to ebay and kijiji, I am trying to avoiding the cost of machine shop cleaning and I have no friends with sandblasting equipment, and most u tubers have nothing or anything going on or they use stuff we can't buy in Canada.
The exterior grease is no problem, but I have had no success with the intake and exhaust runners and lower insides.
Tried using a number of cleaning products for about half hour short time trial period since they are made of aluminum.
Spray 9, Simple Green, Super Clean, Totally Awesome, Pine Sol, Mr. Clean, Orange cleaners, brake cleaners, etc, no success at removing these black deposits.
I tried to avoid the use of 3M green and purple abrasive pads because of silica deposits.
Anyone with first hand knowledge of a good product or procedure that I could use.
Thanks

Never used it myself but heard oven cleaner does a decent job (yes I've also read on the net to never use it). If it leaves outside of the intake looking white / stained, shot of grey hammertone paint makes it look fresh n new plus stands up very well (we use it alot).
Vid I found.

https://www.youtube.com/watch?v=cCjO8JThVpo

Thanks, I have seen this video, but I was under the impression that UK / Euro products are different than US based oven cleaners wheel cleaner, etc more tree hugging over there.
Will give it a try and report back.

Oven cleaner is VERY caustic. I’d caution using it on aluminum. It will clean it, but will also turn it black. Which is fine if you are going to shoot it with paint anyway.
Aluminum wheel cleaner might be safer?

Stock intakes ...not worth much cleaning up IMO.

You could try aluminum brightener, I got some from NAPA, just make sure you rinse well

Please note I have never tried this but I would imagine aluminum wheel acid solutions should do the trick. Spray on, let dwell and then rinse very thoroughly. I have seen great results with the most caked on BMW brake dust come off 8 year old wheels so I would imagine it would do wonders on an intake.

Again, I have never tried it but it may be an alternative.