For some reason my fuel pressure is low, I believe its the reason for the backfiring thru the intake, stumbles, and LOW power. It hangs out around 39-40 psi, and 41 with vacuum off. I have racetronix #32's and racetronix pump. I have a stock regulator. I just put a new filter and the hotwire kit on for the pump today and still no changes. When I give it gas, just easing into it the pressure goes down. I was watching some of the sensor activity on the scanmaster and the map sensor goes down as well when you give it gas. Is that normal map function?

 

Your pressure seems ok to me. 41-47 is the spec with the vacuum hose off. You might be on the low end but I don't think it is your issue. Sounds more like in the opti direction.

 

As you open the throttle body, MAP should increase. With your cam, I would suspect you are not seeing much more the 15"Hg at idle. At WOT, MAP should approach 30"Hg, assuming you live near sea level.

Have you read the MAP section of my Scanmaster guide?

Scanner Guide - LT1

As Rob indicates, your fuel pressure appears to be within spec. Is the 39-40psi at idle with the vacuum hose connected? Typically, you want to see 43.5psi at idle (41-47psi spec limits, as Rob indicates) with the vacuum line off, and pressure will drop anywhere from 3psi (large cam) to 8psi (stock cam) when you hook the vacuum line back up. Seems like you are not getting much in the way of vacuum at the end of that line. Is it possible the vacuum line is cracked?

What is your MAP at idle? What does the Scanmaster indicate as BAR?

 

Not saying it can't be bad too, but I just put a new gm opti, plugs, coil, and coil pigtails on bout 3 weeks ago or so. I still have the same symptoms for the most part as I did before. Still seeing knock and power so low it will barely even spin if you hit it from a dead stop

 

Map @ idle hangs out around 19-20 Hg. Barometric pressure is 29.86" Hg/ 101.1 KPa.
I put all new silicon vacuum hoses on when I did the opti swap. Oh those readings were thru datamaster btw. Let the engine get good n warm and they still read the same. When does the car go into open loop? Mine was in closed from start to finish.

 

The PCM starts in open loop. In order to go into closed loop, three conditions need to be met: 1) coolant temp above about 140*F; 2) O2 sensors hot enough to work (~600*F); 3) timer from start times out (typically 205 seconds). There are flags in Datamaster than indicate, "closed loop (enabled)" (indicates the three conditions have been met), "BLM enabled (indicates PCM is operating in closed loop and adjusting the ST and LT fuel corrections based on O2 feedback) and "Power Enrichment Enabled" (indicates the RPM/throttle position is high enough for the PCM to ignore the O2 feedback and enrich the mixture for max power and torque). When it goes into PE mode and ignores the O2 sensor feedback, the flag will still indicate "closed loop". That just means the three conditions have been met, not that it is remaining in closed loop when it goes into PE mode.

 

any idea why map and fuel pressure goes down as you give it gas?

 

How long has it been since you installed the pump?

 

Just figure out how to post your data log on an FTP site, and there are several people here who can help you out.