Advice for everyone:
- Do NOT go WOT in 5th gear at 90mph. Ever. You shouldn't be WOT in 5th gear unless you're going 130MPH. WOT at low RPM's and high gear puts a lot of stress on the motor, and is also very likely to overboost. Stop being lazy and downshift!
- Get a real tune. The off the shelf tunes are OK, but they are never the best. If you're overboosting, then use the Low Wastegate Tune that COBB offers. But really, just get an actual tune.
There are 3 things that contribute to uncrontrollable (ie. no amount of tuning can fix) boost creep on these cars:
- Free flowing downpipe
- Free flowing intake
- Cold weather
Some cars seem OK with all 3 of these, but some will have issues with just 2, or even 1 of them present. The best thing to do is start by getting a real tune. If this does not help, you have 3 choices.
- External wastegate
- Port the internal wastegate
- Remove one of the free flowing intake/exhaust parts and put on something more restrictive
The last one is usually the cheapest (just put a stock part back on), but if you really want the best flow and still keep your boost control then something has to change in the stock internal wastegate system. Either it needs to be opened up, or you need to bypass it with and external wastegate. Both of these are pretty expensive and do require tuning.