3.2 to 3.4L twin plug conversion

Michael asked about my twin plug conversion experience so I've started another thread.
I needed to rebuild my '86 Carrera 3.2L motor when #6 rod bearing "walked towards the light" one day at the track.
Performance
The displacement increase should have made around %6 more horsepower by itself.
I am very skeptical of all performance claims, if it hasn't been measured I frankly don't believe what I'm "feeling". I didn't get a chance to dyno the car but on the track the car wailed! The year before at Watkins Glen I was doing 120 (indicated) at the end of the rear straight (OK, I'm slow  ) with my old motor (3.2 w/Euro pistons). With the 3.4 twin plug I was already doing 120 at the beginning of the rear straight and 129 at the end. The car was unchanged except for the engine upgrade. My laps went from 2:30ish w/3.2 to 2:23's w/3.4. Some of that was driver improvement (or at least I'd like to think that!).

Parts
- To convert to 3.4L I used 3.2 (95mm) cylinders that had been bored out to 98mm and replated along with "10.5:1" CR JE pistons.
- I used an Andial splitter box from Rennsport (Steve Wiener)
- I got a custom chip from Cyntex via Fabspeed
- I modified my '86 DME to accept the later chip (unsolder and resolder some jumpers)
- I had the same guy who does my heads twin plug them. (Atlantic Enterpises in NJ)
- I used 10mm nuts that take a 15mm wrench for the head stud nuts that would interfere with the lower plugs.
- I did the windage mod to the case webs with a Dremel tool and a burr.
- 964 oil pump
- 993 distributor
- OEM style upper spark plug wires and 993 lower plug wires.
- Stock exhaust with gutted cat. (NH smog rules, has to pass visual inspection.)
- I'd hoped to use 964 lower valve covers since the cam towers of late 3.2's actually have 964 part numbers. I was only able to find some used 993 covers so I used them. Though they looked like they fit (once the stud holes were enlarged) they leaked so I used normal Carrera covers with holes drilled in them. I'm going to try 964 valve covers in the future.
- The twin plug distributor interferes with the plastic duct that goes from the side of the engine fan up to the heater blower. A friend and I removed the duct and clamped it with some blocks of wood and then heated it up with heat gun to give it a factory looking bulge that clears the distributor. I was really proud of the way it came out.
- The new twin plug distributor is also in the way of the plastic duct that feeds air from the blower motor to the heat exchangers. I modified the inlet of the stainless "T" that feeds air to the heat exchangers and made a new hole in the engine tin for a length of heater hose. This was not totally satisfactory. (The hose is just jammed inside the "T" instead of being clamped on the outside and blows out sometimes.) I wound up not using the plastic elbow in the picture, it interfered with the motor mount.

Now, the Bad News

- The pistons broke up before the summer was out. Apparently the motor went lean.
- I should have skipped my track event until I could dyno the car and check the mixture at WOT. I tore it down after 4 days at the track running on Sunoco 94 (to fix some leaks) and it looked fine. I put it together and went to Canada for my next event. I got less than 2 runs in on the local 93 octane and the engine was toast. Another guy toasted his JE pistons in the same fashion at the same event. (Race gas was $8 a gallon at that event.)

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