The ECU makes assumptions based on the car's original equipment.

Changing from a 62mm to a 68mm throttle body increases the amount of air that can be supplied to the intake manifold by 20.3% (3019.1mm^2 to 3631.7mm^2) which might be changing the fuel-to-air ratio.
(or it could be a vacuum leak.)

This is the reason tuners have programmable ROMs in their car's ECUs and do dyno work to map the fuel-to-air ratios correctly for their modified engines.

A couple of other things to do _before_ you heavily modify your car's engine/horse power(HP):
-upgrade the car's suspension to handle the additional HP
-take a real road track training class (more HP means you can/will get in trouble _much faster_ than you did with an OEM car.)