Should the oil injectors hold vacuum.

 

Yes! They must hold vacuum but pass pressure. In my case (89 turbo) they did not hold vacuum and I had FUGLY plugs in as little as 2000 miles. This was soon followed by random detonation under boost! So I decided to go premix and removed all the stuff that delivered the oil. Now the car runs great and the plugs look like they ought to.

FWIW: When I did this I just put four bolts in the OMP outlet ports. This destroyed my OMP in about a week (worm gear inside siezed). I had to pound all the mechanicals out but leave the stepper motor & position sensor active so the ECU wouldn't throw codes. To avoid any futher damage I placed a block-off plate between the OMP and the front cover and just bolted the whole thing back on like it was still in use. Works great! I highly recommend using the block-off plate between your undameged OMP and the front cover in case you ever want to use it again. This will require some dissasembly. If you need help I can elaborate.

 

Great to know this works! I know I have been asked about this in the past but never got a 100% answer from someone who actually did it Thanks for the FWIW!