Hey Stoian21, my feedback may not be perfect since i'm driving a C7.5 which has a slightly different motor and ECU but my experience with APR, 034 and IE might provide you with some valuable insight.

034
EXPERIENCE: They make great products but they have horrible customer service. No phone support is a major issue for me given how much money we spend on some of their parts. When i had an issue with their tune (ECU & TCU), i had to email then, wait a week for response, reply, wait another week for response, reply again, wait another week... 3 week in and zero progress or resolution only for them to say they didn't have the ability to data log my car and the process was likely to take months. I know they offer a more developed package for the C7 so you'll probably be ok, but i hate bad customer service and in my 17 years' experience buying parts from them and going to their Fremont CA location their customer service has never been good.

TUNE - ECU & TCU: When they worked, they felt very good. I especially liked their TCU tune. IF their tunes didn't have issues on my car and IF they had been able to resolve the problem quickly then i would likely still have them on the car.

CONCLUSION / TLDR: When it worked, it felt great. When i had a problem, it felt like crap and their customer service is so bad they could not fix it. If i wanted to work with them via email for 2 months they may have been able to fix it, but that is unacceptable to me. I returned their tunes.


INTEGRATED ENGINEERING
EXPERIENCE: The moment i flashed the IE ECU and TCU tunes on to my car, all the problems i was experiencing with the 034 tunes vanished. The car just worked. They have phone support and are very helpful. Complaints on service.

TUNE - ECU & TCU: I really like the ECU tune and i am still running it. Their TCU tune felt good but it is more conservative than 034 and i wanted something more aggressive. Don't get me wrong, their TCU tune is still WAY WAY better than stock, but i can drive... hard. I switched over to the Melen TCU tune and love it. IE ECU and Melen TCU tune is fantastic.

CONCLUSION: Great ECU Tune, Good but sporty TCU tune and good customer service.