Minimal Vacuum at idle

[PKRWUD]

Wow. Code 98. I don't see that one that often. It means there is a major failure with one of your sensors. When this occurs, the ECM disregards the info coming from that sensor and substitutes a pre-programed signal until the sensor is repaired or replaced. The way to determine which sensor has failed is to run both KOEO and KOER self tests, and the bad sensor will be identified. In your case, it's the MAF. Your MAF has failed, and the ECM is substituting a predetermined value in it's place (aka: "limp home mode"). Problem is, unless the ECM has a chip that was custom burned for your mods, it's defaulting to a value based on a stock engine. This means the ECM thinks you have 19# injectors, a stock cam, no blower, etc. The results would be a no-start or very poorly running condition. That being said, 2 inches of vacuum still seems way too low, even under those circumstances. The only thing I can think of is maybe your blower is creating boost at idle. I would check it and verify that there is no boost at idle, and then replace the MAF. Once the MAF is working properly, the code 98 will go away, and the ECM will accept real signals as opposed to preset ones. Once the code 98 is gone, your driveability should be restored.

Take care,
-Chris