The 4G63 ignition transistor module looks like this.
The part number on the heat sink is MD149768, it's a bit hard to read because I shrunk down the picture.



I picked up this one for $10 at my local junkyard, it works like it should.

It's pretty easy to lift one of these from a 4G63, it's bolted to the right side of the head only a few inches from the coilpack.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)