Your setup sounds like you should stick with 6's.

I'd guess the sensor for that vacuum gauge is headed south.

I can't really help you with this one but i could not find any other posts about this. I have a 1g and the stock boost gauge jumps irratically like yours with a weird idle to go along with it. The weird thing is that my aftermarket gauge doesn't move at all. No one seems to have any ideas. Have you figured out what your problem is yet?

No. It's really sporadic. Sometimes it's fine. I also noticed that it does it when I'm say... in 4th/5th gear at over 70mph. It will hit max boost and then fluctuate insanely between 1/2 and max boost. I don't even think that's possible... So, I'm starting to think the sensor is just going to hell.

No. It's really sporadic. Sometimes it's fine. I also noticed that it does it when I'm say... in 4th/5th gear at over 70mph. It will hit max boost and then fluctuate insanely between 1/2 and max boost. I don't even think that's possible... So, I'm starting to think the sensor is just going to hell.
there is several things that could be causing you situation. first of all it could be a boost leak from the bottom of your intake manifold where it connects to the head. i say this because it is extremely difficult to locate this possible boost leak because it is extremely difficult to access that portion of your engine. its also difficult to spray soapy water to see if it bubbles, without removing your battery and throttlebody components. it can be done of course but its a pain in the ass. Secondly, in regards to your issue in 4th and 5th...
son of a biach this thread is six years old, but in regards to the high potential of dsmers that may have the same issue i will quickly finish.
.........where boost on gauge flucuates from fulltohalf boost this is called boost creep, but also for 2gers our ecu advances the timing when the air fuel ratio or knock possiblilty is not correct. if you have a leak which i think you do your turbo gauge says say 15psi and is actually running around 20psi. find the leak at all costs becuase a car running rich is a car running slow.
check your plug gapping should be the bpr6's and gapping between 28(aftermarket or lightly tuned setup.)
factory is 32. i do mine at28 with a 1 handicap. it all depends though. you will need the bpr7 somewhere around 350 on aftermarket internals.
the plugs and wires would be where to start if it continues after you fix a boost leak test.

Check the time stamps on threads before you reply to posts. The last post was from 2004

It kinda helps to post even if a few years later. Problem never resolved. What if I needed the answer now. So I say post on