So you are saying the vortec pump is the issue? We just discussed this earlier in the post.
I'm saying you need to know for sure what the fuel pressure is with a confirmed accurate gauge. 20 is too high, unless you have a tune that requires it to be that high. Spec on that TBI system was 9-13. They don't like 7, and they don't like double the pressure at 20 either. If it reads 20 and your gauge only goes to 20, how would you know if it was 30 or 40?
I'm not saying the Vortec pump is your problem. I never tried one in a TBI system. Maybe it will work. Maybe the fuel pressure regulator will dump all the excess flow back to the tank no problem. Maybe it won't. As I said, I never tried. But I can say that those engine's computer system doesn't like 6 or 7 psi of fuel pressure, so there is no reason to believe they would like 20 psi or more. Understandably, 99.9% of the time we would see low fuel pressure problems on TBI systems as opposed to an excess of pressure. But I have seen several MFI systems with excess pressure, and they didn't like it at all. At all.
What I have done is repaired thousands of those trucks and TBI systems on other vehicles through 35 years as an ASE Master and Advanced Driveability Technician. They always ran great as designed. Personally, I would rather have a "K" motor TBI system over an "R" motor MFI any day of the week as a daily driver personal vehicle. They were far more dependable, cheaper to maintain over the life of the vehicle, and will usually run far better at 150-200,000 miles than an MFI vehicle because of injector variances that build up in 8 separate injectors over time. And I wouldn't trade off those benefits for all the expense of ownership that come with the Vortec system for a 20 HP difference.
In theory the TBI regulator could handle some increase in potential pressure and flow and still maintain 13 psi. I don't know how much, or if a Vortec pump exceeds that.
In this case, I figure your 20 psi reading could be due to an inaccurate gauge, or real excess pressure. I've had previously known good gauges start reading incorrectly, temporarily leading me in a wrong direction. You need to nail this down first to diagnose your issue if you want your truck to run properly.
Tom
