Remove the tuner and throw it in the nearest trash can. Adding/subtracting fuel w/o the aid of dynamometer equipment to test it out is like guessing lottery numbers

 

Because it's only happening at higher speeds when fuel demand is highest, my guess is fuel pump/pressure related. The fact that you recently got a new fuel pump adds to that suspicion.

It may be that the fuel lines in the tank have a small hole in them or something like that.

 

Because it's only happening at higher speeds when fuel demand is highest, my guess is fuel pump/pressure related. The fact that you recently got a new fuel pump adds to that suspicion.

It may be that the fuel lines in the tank have a small hole in them or something like that.

I was having the issue before I replaced the fuel pump, that's what led me to replace it. Part of the replacement was the in-tank fuel line, so there should be no leaks there. If there is a leak, it would be outside the tank, in which case I think I'd have a noticable leak.

The only thing I didn't address is the internal fuel filter. I've read that they can plug up...

 

May be last things for check are injectors. Clean them and try again.

 

One thing that’s easy to check is that your throttle cables aren’t hung up outside their fittings. The short cables coming from the plastic distributor box under the tank and leading to each throttle body cam can easily get dislodged and now you have an imbalance between left and right. Also the cables can slip off the cams under the throttle bodies (can be checked with a small mirror), not to mention that these cams are known to crack from old age, but if they do break I suspect you may have bigger symptoms than what you are describing.

 

I'll check that, thanks!