Ok so i finally got to take a look at the tune file for you, the assumption that the overboost was kicking in is absolutely correct.
Here is a small snip of the log file from above, lets take a look at the status bits and decipher the information.
as you can see at 382s into the log you hit 220kpa and then status bit 2 shows bit 64 = overboost protection. The status bits are a fast way to see what state the ecu thinks the engine is in and then you can start to decipher why.
lets take a look at another status bit for a moment, this one is still under status 2 but I am looking at bit # 128 this time. 128= CL idle, I see you have a hanging idle issue so lets take a look at that.
Looking at this we can see the top graph the rpm drops 250 down to idle after a delay, lets find out why.
- The red arrow shows status 6 = 96... this does not apply to any of the basic bit fields, they count from 1 and double with every step
1-2-4-8-16-32-64-128 so when we get a number between this value that means we have more than one status bit active at one time.
96= bit 64-fan is on and bit 32- idle advance is active..
We can see in graph 3 the timing going to the value used in the idle advance page when status 6 gets bit 32 active.
- The Blue arrow coincides with Status 2 bit 128- CL idle is active, now why did the idle not become active sooner? you are coasting to a stop a hanging idle is aggravating. Well the purple arrow is looking at the VSS input to the ecu and under engine states in your tune you have the idle locked out until the car is at a speed lower than 3MPH.. this is the cause of the hanging idle. This however is not a terrible thing and will eliminate stalling issues, but personally i think a lower value would be great, IMO lowering the IGN1 timing table in the area of idle down to say 15* will help fix this issue.
I am posting a tune file for you, with some changes. I feel like you are working harder than you need to on the fuel table, so i simplified it into one table from two. Once the majority of the tuning is done we can break them back out again.