There have been a lot of questions lately about doing Emissions system deletes on the B5 1.8T. User "absolutegtr" did a very nice writeup for the B6 1.8T guys here:
There is nothing quite like it for the B5’s. I hope this DIY writeup will stand in that gap.
Simplify the under hood vacuum system.
Identify specifically what does, and what does not cause DTC codes (and subsequent Check Engine Light illumination).
Get rid of "all those check valves", after first understanding what they are for.
Note 1: There are differences in the vacuum and pcv systems between almost every year of the B5. I will do my best to identify the differences. That said, most of the deletes discussed here will apply to the 2000+ cars. The 97-99.5 AEB emission system is already pretty simple as it is.
Note 2: Since this is something I did a while back, it won't be a step by step type of thing. You can rip this crap out it whatever order you deem necessary and effective. Onward.
For each system, We will first take a look at the factory setup and determine what exactly we want to remove. We will be going through the systems in a piece-wise fashion for those that only want to delete certain parts. The following will be covered in order:
1. Secondary Air Injection system
2. N249 (Electronic Control of Diverter Valve)
3. Suction Jet Pump
4. Vacuum Reservoir (constant vacuum source)
5. Evaporative Emissions
6. PCV refresh
*If there are any errors in anything I've shared, extra information that should be added, or crap that I just plain got wrong - please do not hesitate to correct me on it. This is meant to be a resource for B5'ers, so your input is appreciated.