I'm guessing you're young & excited & have big Capri dreams. I was there once too
Did you read about thread about the turbo conversion? I know you don't want to hear it, but it is significantly cheaper, less work and less heartache to find an actual XR2. It's capable of handling decent amounts of power from the factory. The N/A is not. There's a lot of folks who have gone the same exact route you are going down, and have ended up buying an XR2 or leaving the Capri platform altogether.
A stock XR2 makes 132 crank horsepower. Thats ~115 to the wheels.
A stock XR2 engine is enough to kill an N/A transmission.
150 is at the very edge of what the N/A transmission will handle, IF you baby it. And let's be honest, who wants to baby it?
Even the stock XR2 transmission does not like abuse. Burnouts are the #1 killer of XR2 transmissions. You mentioned converting to XR2 trans- thats a lot of work by itself! Flywheel, clutch, mounts, axles & intermediate shaft, clutch cable, pedal assembly all need acquired & swapped out.
The Megasquirt is not a chip that installs in the stock ECU. The Megasquirt is a total ECU replacement - you remove the stock ECU and the Megasquirt takes its place. It's configurable and tunable in every way, and once you get it setup it's relatively easy to tune. There are even MS units that will plug into the stock engine harness - but these are not ideal if you're really going after performance.
Use Photobucket or IMGUR to upload pictures, and then hotlink the images here - the forum does not support direct uploads at the moment.