So I know that both the Illusive man and Saren had reaper implants, but I was wondering if there is any point in time that Shepard could have acquired them. Perhaps when Shepard was being rebuilt by Cerberus?
At the point in time of shepherd being rebuilt, Cerberus and the illusive man thought the reapers were the enemy, it isn't till about 1/2-3/4 the way through mass effect 2 that the illusive man stops thinking the reapers are the enemy
TIM and Saren were indoctrinated around 2157 and 'improved' during ME3 and ME 1 respectively. Their behaviour against the Reapers was part of their indoctrination.
Speaking of which.... the Prothean VI's Vigil on Ilos and Vendetta on Thessia were able to recognize and identify Reaper Tech and Indoctrination. They spoke to us voluntarily, so no, Shepard has not been improved by Reaper Tech.
As a Sidenote, the former storywriters hinted, that it was originally planned for Shep to choose Reaper Agumentation to fight the Reapers, as without it would not have been possible. It would habe been a complete different story with Dark Energy as it's Core.
But that's fiction now, as the game developed differently, as we know, hate, like, except, suffer (to each his own, feel free to pick one).