Holy cow, I had no idea you just left the plug out completely!!?! I figured you were just using that to open up the channel you blocked off. As you found out, any 'leak' after the MAF really screws with the fueling (since the air isnt being measured, it's not being fueled for) plus all the random dirt and debris in the engine bay will get sucked right into it.

Again, I dont mean this to come off as rude, but I think it's better to put the dremel down for awhile and spend some time learning the fundamentals. It seems a little crazy to start hacking and plugging random stuff when you dont have a handle on the basics of how the part you're modding works.

Plus with a 3800, there's plenty of proven bolt on mods out there to make more than enough power to keep you happy in the short term. Once you're bored with 500-550+, then it makes sense to start digging into oddball projects like this to squeeze a little more out.