So I bought an Evo 8 w/ almost 120k miles fully expecting issues to pop up here and there. Then as I'm driving, I hear a brief gargling sound and my engine starts idling at 1.25rpm (pretty steady at 1.25 but random sputters to 1.5) then four codes pop up:

P0300: Random/Multiple cylinder misfire detected.
Secondary:
P0113: Intake Air Temperature (IAT) Sensor Circuit High Input Problem
P0107: Manifold Absolute Pressure (MAP/BARO Sensor) Circuit Low Voltage
P0121: Throttle Position Sensor (TPS) “A” Circuit Range Performance Problem

I check the spark plugs and they're all toasted. Black soot all over. They're only a month old along with the new timing belt job and new valve cover gasket. I have new OEM spark plug wires waiting to be installed. Pretty sure I'm running on OEM fuel injectors. I check the MAF sensor and it has a little gunk building up on it, but overall looks fine. Compression test came out all at 175. The previous owner did have it tuned to 320whp but I was planning on bringing that down with the current setup the way it is.

Now my question is: what could be the issue? I'm leaning towards a vacuum leak at the moment. Any insight would be very appreciated.

Mods:
Stock BOV, Injen Short Ram Cold Air Intake, HKS Catback, unknown aftermarket downpipe.