evolutionuk24

I HAVE A 95/6 IMPREZA WRX STI IMPORT. WHEN MY CAR IS COLD IT'S FINE BUT AFTER IT GETS HOT AFTER 10 MILES IT HAS TOTAL LOSS IN POWER AROUND 4.5 TO 5.5 GRAND, REV COUNTER DROPS TO 0 EVEN THOUGH THE ENGINE IS SPINNING. CHANGE UP GEAR AND IT PULLS AGAIN AND CUTS OUT. EASE OFF AND THE THROTTLE AND REV COUNTER COMES BACK AND THE POWER IS BACK. AT THIS TIME I'M ALSO TRYING TO GET IT THROUGH ITS YEARLY EMISSIONS TEST AND THE CO IS TOO HIGH. I'VE GOT THE ORIGINAL AIR FILTER BOX ON CAT AND ORIGINAL BACK BOX

THE ENGINE MANAGEMENT LIGHT IS OFF WHEN COLD AND COMES ON AFTER I'V DONE 10 MILES AND JUST AS IT'S CONNECTED TO CAT TEST MACHINE AND HELD AT 2500 rpm's IT COMES ON PLEASE CAN ANY ONE ADVISE ME HOW TO SOLVE THIS PROBLEM (sorry about CAPS)