I have a 98 z28 ls1. The fuel pump went in it about 3 months back. everyone told me to replace it with a Walbro pump. So I did...I had a 255 Walbro put in. It worked fine for awhile....although ever since the new pump was put in it took a little longer to turn over when starting it up..like it wasn't getting quite enough fuel. But that could just be because it is a higher pressure pump it takes longer to build up that pressure...at least that was what I was told. But now when your doing like 65-80 in 6th driving normal the RPMS with drop ...almost like it is having a harder time doing that speed than before. But if your racing it will do it just fine....in fact it will do 110 just fine. Acceleration is 100% though. You can burn out for quite awhile in it...just as it has always been. Gears 1-6 are more than happy under heavy acceleration. It is just the everyday driving it doesn't like as much. Which is what is leading me to believe it is a fuel pressure problem. I don't trust 110% the dude who installed the pump so I wouldn't say that there is no way he didn't mess up the job...I don't know if there is something he could have messed up in the proccess of installing it, or if it could be the pump itself. I replaced the filter just the other day...no change either. I put on an SLP Loudmouth II cat back on a month ago, and a SLP lid as well....but it doesn't seem like an intake or back pressure issue....but I am at a loss as to what it could be...just had baby so we no longer have the time to mess with it dispite it being a great car. I am about to sell it and cut my losses. I put so much work in this thing, and it has so many new parts....but I like I said...just no time. But Id love to figure out what is making it do that, or if it is just our imagination.. ANYONE HAVE ANY CLUE WHAT THE PROBLEM COULD BE?!?!?!?!?!