I swapped in the engine from my e30, a 2025cc M10 with L-jetronic. It was built in 2003 with 9.9:1 forged pistons and a stock 1.8 head
AC compressor is gone so the battery was moved across to make room for the AEM cone filter. I welded an extra alternator mounting arm to the side of the car for attaching the AFM. I used the alternator and starter from a 533i. Note the adjustable fuel pressure regulator and the red lever for idle speed control.
I converted the M10 to a distributor-less ignition using the Megajolt Lite Jr. control unit and Ford EDIS ignition module and coil pack. Since I am only using the outer-most row of my crank pulley, I welded a toothed ring from trigger-wheels.com to the inside lip of the second row. The VR sensor mounting bracket was fabricated from scraps and attached to the bracket that holds the PS pump on an e30.
Here is the ignition map I have been using since 2011.
I also replaced the small 45mm throttle body from the 318i setup with a 50mm 325e throttle body. I had to grind two of the bolts holes and make a metal insert to go between the TB and intake. Then reroute some hoses and modify the linkage. (318i TB on left, and unmodified 325e on right)
On the exhaust side, an e30 manifold fed Magnaflow downpipes/cat and a Magnaflow 12644 muffler with 2" stainless connecting pipe.
The e21 suspension was modified with Bilstein sport shocks, stiffer springs (cut springs from other cars, roughly double the stock rates) , urethane rack bushings.
After ten years I finally had a chance to run the M10 on a dyno. It seems to be on par with a euro 2.0l, and with an amazingly flat torque curve. No doubt, a camshaft could have unlocked some more power from this setup.
Sadly, by this time the car had completely rusted-out rocker panels, widespread failure of the undercoating, and rust in the rear shock towers. I had to part with it. :(