Boost Fluctuation

[aminga]

Not that this is your issue, but that little stock 25 year old turbo does not like 20 psi and is out of it's efficiency range. Yes it can do it, but that intercooler is struggling to cool that super heated air.
It's possible that this is the cause of a lean condition. 750-780 wot at the top of third is perfectly acceptable using narrow band.
The exhaust pressure is likely overcoming the waste gate spring and pushing the flapper open at 20 psi. I recommend an HD waste gate (which I believe starts at about 18 psi) shortly followed by a turbo that can reliably support 20+ psi. The turbo is the weak link in your combo.....that and a stock transmission. You have most everything else to support more power.

Mike, I missed that. My stock turbo would only go to 18psi.

 

[Ttype6]

It's his choice, his car. I put 20 years of experience into my suggestion and that's all it was. Sorry if I came off like a dik. Rereading it, it seems I might have.

You said that his turbo is running at the upper end of it's limit and that's true. It's,probably,worth nothing to go higher. The standard adjustable actuator would solve his problem and allow him to lower his boost when not using higher octane.
If he's like so many of us,he can't wait to find out how his motor runs with higher boost. I was offering him a way to do it this weekend. I know how frustrating it is to find a possible solution to a problem with your car and not be able to implement it on your days off. The adjustable actuator could be purchased in the future.

I hope you can see how important it is to be able to lower the boost if you run gasoline. I wouldn't want to have to buy 110 all the time.
Now that I run E85,I could use the HD actuator and not worry about it's inability to allow lower boost,but I already have something that works.

Many people come off looking like dicks. Few would,ever,admit to the possibility of that. We all can,have,and will do it from time to time. You are forgiven my friend.

 

[mtbraun]

Thanks everyone for the feedback. It was very helpful. I am going with an adjustable actuator (HD) with my turbo upgrade this winter.