996 idles fine but dies when you touch the throttle

Hi guys,

last week i was at the track and sadly am now not a virgin to the tow truck bringing me back.

I was accelerating down the front straight and my 996 skipped a beat and then that was it, pulled the clutch and rev's went to 0.

Now week or so on, I found the single 15amp fuse that was for the ecu relays (under the seat) was melted but not blown.I have changed the ECU and back end loom (now has 2 fuses for the ecu relays( a 5 and a 20amp)
((but still running the same eprom as only at present until the new one arrives have only one)))
I have great spark, and i can make her idle great, but when i go to touch the throttle she dies, and it's not a splutter sort of dying but a dead stop rev counter goes to zero and dies. then i can start her up again just fine. but again when you go to touch the gas......

(( i had an issue with spark being that the sensor that runs the timing had a gap that was a touch too big,have shimmed it and spark is strong.

I have spare relays,ecu ones, plus the ones beside the battery, have one by one changed them all.

Am i missing something?? Has anyone heard of anything like this before?

Do i need to try brand new relays?

I'm a touch frustrated and also extremely stumped !!

Any ideas welcome.......