Ok 96z28 ,mods are magnaflow catback,tb bypass,cold air,maf translator,30 svos,airfoil. Thats pretty much it for engine mods.60,000 miles.
I have wierd problem. As I floor the car taking it up to 120mph or so it gets leaner and leaner and leaner on my scanmaster. Going as low as 700s on the 02s today. Yet I saw no knock. I have watched both 02s today and they both went to about .820 on quartermile run. I have played with base and wot on my translator with no apparent effect. The car seems to do exactly the same thing. Have watched both 02 sensors and they do identical things and give near identical readings. I have zero check engine lights. Car seems to run pretty smooth but did seem to be fighting at higher rpm sort of hitting a wall. I have checked fuel pressure and its like 48 line off and 38 line on.I have watched fuel pressure as make 1/4 mile or 120mph runs and it stays constant ,buddy was watching it but it was around whatever it should be he has a built 383 and knows his lt1s.
My fuel pressure reg acts normal when you plug and unplug the line. My injectors are suppposed to have only 5000 miles or so on them. My other stock injectors did the same effect on the o2s. My 02s are I assume original
but they do cycle like they are supposed to but just can't seem to get them to stay up for 02s.
The car runs not bad thru the quarter today according to my tazzo but should rip the tires off with my 3.42 gears and 2800 vig. It doesn't .It don't feel fast. The tazzo mph wasn't too bad showing 100mph or so and times of 14.0 best I think it was with a 2.26 60ft but what is up with those stupid low 02s?
Can the pump put out proper pressure but not enough volume or something?
I haven't changed plugs or wires yet was waiting to buy a delteq but no misfires showing with check engine lights and no rich or lean codes.
What good is this obd2?
I am going to be switching to my granatelli lt1 maf as might have mixed up my ls1 and lt1 mafs and no one can tell me if they are 100% compatible or how even to tell them apart. The wierd o2 thing has been happening with stock maf.
I am pretty sure the maft is working as if it wasn't you would think would be super pig rich. Maybe my maf is n't working. I can only get readings of around 170 max think at like 120mph and not sure rpm.

I tried to put in some newer o2 sensors that got off buddy but not sure how in heck you put in the passenger side ,do you have to drop the exhuast down and do you need a new gasket for drivers side when you do..? My car is stock exhuast 96.

I have new plugs to try shortly. I did have a water pump failure last year but the car seems to run smooth and no huge misses. I just put in a brand new alternator and have a fairly new optima red top.

What is left to check..any tips greatly appreciated.

 

I put in a granatelli maf that I had laying around. Car seems to do identical things..no codes and maf reads aiflow and goes to think it was 160 or so not sure speed pretty fast .02 drop like rocks yet usually don't see any big knock did see 5 counts once though. Saw o2s from 700s thru low 800s. I set maf to 30 per cent lean for my 30 svo. Left wot dial straight up. Car felt a bit faster than stock maf when had the maft set at various times of 30%,25%,20%.

So not sure what to try next. I guess try to swap 02 and change plugs and see what it does if anything.

 

By taking the line off the FPR will not tell you anything about the pump. Once the RPMs climb and then engine start using up the fuel and the pump can't keep up the Fuel Pressure will drop, you need to make a run and watch the fuel pressure at high RPM, I bet you its dropping.

No matter what you do to the injectors up top won't do a thing if your fuel pressure is dropping up top.

Also, please note that the faster you go the leaner you get, its like in an M6, in 2nd gear you might read 920 on the o2's but in 4th gear it will be 880 because you're under more load, but your problem seems different since you have an AUTO and it does it according to RPM as well and its dropping way too much. Definately sounds like a fuel pump.

I had that problem, without changing out the fuel pump I bought the Race Tronix fuel pump kit but just used the wiring harness which takes 30 mins to nicely route and plug in without taking out the pump. That solved all my fuel problems because the harness boosted the voltage at the pump by over 1 volt.

Eventually I put in the racetronix pump for the hell of it since it was sitting here, but the stock pump with the racetronix wiring kit was all I needed for my 420 rwhp.

Now once the pump situation is fixed, then look at your TC lock up in your tune, if you tune you A/F with the TC unlocked, then by the end of the 1/4 mile track your TC locks that will cause you to go leaner as well.