So is it chippable?
OH YES !!! and without a Maf There are certain other areas tht can be played with without the Maf pulling it back down!!! 
You been buggering with the crude waste gate setup?
Please tell me more!
Imagine the simplest most crude waste gate setup you have ever seen and then simplify it!
On the diseasel, the waste gate is normally closed and only opens as the boost pressure increases. The actual actuator is fed off the turbo boost pressure so as the inlet pressure rises, the waste gate opens therefore reducing the turbos rpm and maintaining a constant boost.
So, if you bugger about with the waste gate actuator then you can up the boost........dont overdo it though or you risk over revving the turbo!
Heres where it gets a little more difficult though, around 1997ish, a MAF was added to the setup to reduce smoke on full chat (to meet the regulations that were coming in) and this monitors the airflow. If it gets a bit high, it backs the fueling off to stop unburnt fuel exiting out the back James Bond style in a cloud of black smoke (because the smoke you see is unburnt fuel!)
This 'improvement' makes it harder to tune the old slug as your always fighting a few lines in code that are backing the fueling off!
Only, they didn't do a very good job of it

- "My name is Boy, The Boy"
Actually, I keep forgetting to plug the MAF in on mine. Tends to stay that way for weeks. First thing I notice is a stored fault code if I plug Tech2 in...