First of all my STI has these Xcceleration mods on it currently (Dastek piggy back unichip, boost control module, short ram intake, manual boost controller, new wiring harness for the piggy back, and their custom 3" exhaust) and have had them for a little over a year With no problems. I'm not completely certain the exact date they were put on, but I am the second owner and do not know the original owner only know that this is what he had on it when I purchased it. It currently has ~30k miles on it.
The STI had a wierd problem one day with a fuel cutout symptom(hesitate randomly when accelerating/slight jerk) and I was really kinda afraid to drive it, but the hesitation only lasted a couple seconds then went away. Then the next day I was pulling out of my driveway went about 15 yards to a stop sign and the car completely shut down almost as if the keys had been taken out.
It would turn over completely fine but would not start. So the battery is fine. I waited a couple of days and tried to start it again while waiting on my friend to get his scanner, and it started up for a split seconds then cut off again.
Then when we scanned it, it threw a p0335 and p0102 codes, crankshaft pos sensor circuit A and MAF low input. I figure the crankshaft pos sensor might have gone bad and is telling the engine to cut fuel and not allow it to start.
But before I could do anymore I already had a vacation planned and was gone for 10 days. Now here is where it gets interesting.
I come home after ten days and just for fun try to start the car. To my suprise it starts up and runs perfect, so I clear the code, scratch my head and decide to take it for a test drive. I let it sit at idle for about 2-3 minutes to warm up then drive it for about 5 minutes at slow speeds (25-35 mph) and just when I'm about to head home I'm heading into a different stop sign and it just flat out dies again, and will not start. Exactly like before.
I'm thinking it is not a p0335 that is the real problem, I'm kinda down to thinking it is fuel starvation due to needing a new fuel filter(yet to be changed that I know of) or maybe even a gremlin problem with the piggy back but I wanted to get some input and see if maybe anyone else has had similar problems before I got too into this.