I don't have a ton of experience with the ME7 cars, but I might have a few suggestions for dialing in the '98.
First is play with the wastegate settings. This can make a huge difference. Tightening it up half a turn at a time can be noticeable and reduce turbo lag. I'm pretty sure stock pressure for the wastegate is 4psi, if you have a tool to check.
Also, two other possible things to help driveability on the '98 are replacing the throttle position sensors and the boost control solenoid. There's a youtube video somewhere on the throttle position sensor, and it shows how these sensors lose readings at certain points over time. He says you can clean them up with brake cleaner, but they are pretty cheap new so I just replaced it. This made a huge difference in my manual car, as the power came on more consistently and it was way easier to smoothly engage the clutch. The boost control solenoid is another one that seems to slowly fade out, instead of just dying. Replacing this solenoid with the newer Pierburg one, that has been suggested here many times (hopefully someone else remembers the part number) gave me a lot quicker turbo response in one car in particular, and again it's fairly cheap so it's easy reassurance that everything is dialed in.
For the boost gauge you can get a bluetooth plug-in for the OBDII and then use an app on your phone to read boost, as well as a bunch of other readings. Obviously this route does not give you a true built in gauge, but you can still check boost when you need to.
First is play with the wastegate settings. This can make a huge difference. Tightening it up half a turn at a time can be noticeable and reduce turbo lag. I'm pretty sure stock pressure for the wastegate is 4psi, if you have a tool to check.
Also, two other possible things to help driveability on the '98 are replacing the throttle position sensors and the boost control solenoid. There's a youtube video somewhere on the throttle position sensor, and it shows how these sensors lose readings at certain points over time. He says you can clean them up with brake cleaner, but they are pretty cheap new so I just replaced it. This made a huge difference in my manual car, as the power came on more consistently and it was way easier to smoothly engage the clutch. The boost control solenoid is another one that seems to slowly fade out, instead of just dying. Replacing this solenoid with the newer Pierburg one, that has been suggested here many times (hopefully someone else remembers the part number) gave me a lot quicker turbo response in one car in particular, and again it's fairly cheap so it's easy reassurance that everything is dialed in.
For the boost gauge you can get a bluetooth plug-in for the OBDII and then use an app on your phone to read boost, as well as a bunch of other readings. Obviously this route does not give you a true built in gauge, but you can still check boost when you need to.
