I have a weird problem with the car. It has the following modifications:

AEM EMS running speed density
HKS 272 with cam gears
Turbo back with hi-flow cat
walbro fuel pump

last night on the way home from work in 4th gear doing about 55-60mph with rpm i think 3K or 4k the car became totally unresponsive to throttle input. upshifted to 5th and it was fine.

Then same thing happened again in 3rd gear today around 3K rpm probably doing 40-45mph on the street..felt a little hiccup and then all of a sudden no response from the throttle for a couple seconds while i tried to figure out what was going on. shifted to 4th and it was fine again.

any clue what that could be? otherwise it drives and accelerates fine. here's what i'm thinking but i could be totally wrong

1) fuel pump?
2) one of the ems sensors going bad?
3) hi-flow cat is clogged?

 

no one?