1986 Chevy 350 EXTREMELY high idle!

Alright, to be honest im no mechanic. I know what the parts are called and have a general idea on what they do but when it comes to fixing it… Oh boy. The reason for me doing all of this was to fix the pinging in the engine when I put my foot down.

But I wanted to take the gamble on adjusting the timing on my 1986 Chevy Silver. Originally it had a 305 engine and in 93 my dad had it swapped for a 350, there is a larger cam in there but I don’t know the size or name of where it came from. Anyway I hooked up a timing light and it was at least around 14 15 degrees. That seemed way off considering my emissions sticker said 4 degrees but I was going to try 0 degrees since thats what most 350’s used. I pulled of the entire airfilter assembly and dove straight into the distributor, I couldnt gain access to the bolt to allow me to adjust it so I thought that maybe that wasn’t what I was supposed to go for. I undid the clamps on the housing and pulled it off. Questioning if I completely fucked up the engine, I put the distributor back together and started the engine. Normal for 1 second and the engine revs to 4000 rpm at least, I don’t have a tacho so I couldnt tell you. And yes I did disconnect the vacuum hose and plug it. Does anyone have any idea why the truck is suddenly idling SOO high?