This has been covered alot in previous posts:
a torque converter really wont help with the shifting problems - the only shifting problem is the auto's tendency to hang in a certian gear - and bounce off the redline between the shift from 2-3. A shift kit may help - but more than likely not. They really dont help the situation completely - for me at least i bounce off still..but for a shorter period of time.
When you start to surpass a certain HP amount - the problem becomes worse and more noticeable.
This is mainly due to the construction and electronic control of the transmission. The A350e is really a 4 speed transmission electronically controlled to have a 5th gear - the extra gear being a 1st gear overdrive - which really is 2nd gear. When you have f/i of any sort - its basically freaking out the transmission.
Pfs systems have found a way around that 2nd gear overdrive with their 'shift kit' but you cant obtain it separately from their turbos.
There are certain members and companies that are working on a way around the overdrive - hopefully we'll hear from them sometime soon.