Car is stock other than gutted airbox w/ k&n filter, and zzp 1.0 pcm which i just purchased. I had the pcm in the car a few days already but I decided to really get on the car to test it out. I got her up to 120 when I noticed my ses light was flashing, I immediately pulled over and turned off the car. I read online a blinking ses light could be a multiple cylinder misfire. I immediately changed my plugs and wires as the first step. Went roughly 3/4 throttle and not only did i get a blinking ses light but now i had a semi hesitation around 3k rpm and grinding / clanking noise coming from under the hood almost light at exhaust rattle sound. When i got off the throttle it went away. I went home took off the */c belt checked the pulley for any slop, it seemed to feel alright. I decided to drive the car w/o the */c belt on. I went 3/4 throttle on it, no blinking ses light, no rattling, grinding, clanking noises. I put the belt back on anyways and have just been babying the car. My first guess would be the snout coupler obviously, my second guess would be the pcm ? I still have my oem I didn't return it yet and it would be an easy troubleshoot on that front. Any other suggestions would be great. It seems to be getting progressively worse I feel that even if i do solve and fix the problem I will most likely just baby the car for the remainder of its life lol. Thanks in advance, sorry it was so long.

If the light is blinking or ON, we need it scanned for codes before we can go any further. Anything else would be purely speculation.

What kind of fuel are you running in it? 87 or 93?

I always use 93

Ok, then we need to get whatever codes are stored in the PCM please.

P0300 Random misfire - intermittent
P0243 turbo/supercharger wastegate solenoid malfunction

Looks like the PCM is trying to dump boost but it can't possibly due to a malfunctioning vac valve.

With the engine off (no vacuum) the rod in the BCA should be fully extended. At idle (max vacuum), the rod in the BCA should be fully retracted. At WOT (min vacuum) it should be fully extended. Check to make sure this mechanism is moving freely. If it is binding it may not be fully retracting at idle which would result in boost when you don't want it. Also, check the vacuum line going to the BCA. If it has a leak the BCA won't receive fully vacuum at idle and may not fully retract.

Best way to check it is at idle disconnect and reconnect the vacuum line from the BCA a couple of times. When you disconnect the line the BCA rod should fully extend. When you reconnect it should fully retract.

I tried this and it seems to be working correctly.

Then we still need those codes. Otherwise, we could be guessing all day long.

P0300 Random misfire - intermittent
P0243 turbo/supercharger wastegate solenoid malfunction