What will 8 quarts of oil do to a FC 13B engine
 

I got a new PLX wideband for my 1991 FC and noticed it was burning rich. The original MPG for the RX7 is listed at 24mpg. I was getting 14mpg around town and 20mpg on the highway.

I thought having an aftermarket computer installed and a dynotune would help get my MPG up. So I drove it from Utah to Lucky7Racing in Duarte, CA. They called me up saying it was ready and I told them I'd be out on September 15th to pick it up. Then I got a call saying it wouldn't start and they were working with Adaptronic on firmware fixes. Then they said they did compression test and it was really bad and the engine would need a rebuild.

I flew from SLC to LAX and then took two hour train to Duarte to get my car. On my way home my EGT was hitting 1700F going uphill at 5000 RPM. It was impossible to drive over 80 MPH without EGT over 1300 F.

After I stopped for the night I checked my oil in Cedar City (about 400 miles driving with too much oil) and found 2.75 quarts of excess oil in my engine. Car ran a lot better after taking out the extra oil, but it still is stalling when I stop at a light and it chokes out around 6000 RPM. The EGT is lower though.

Lucky 7 Racing is saying too much oil would create lots of smoke out the tailpipe. However, that wasn't the case. The only thing that changed is the rear rotor lost compression and it drives like crap compared to when I drove it to their shop.

Question is, what will putting 8 quarts of oil do to a 1991 13B?