I need help, I have a 91 RS with 170000. It suddenly started to surge with a noticeable loss of power and no change in sound. When throttle is reduced from any setting the engine seems to regain some of it's power. The engine also has started to surge at idle. There are times when it won't start, I sprayed fuel directly into the intake once, and it started right up, after this I changed the fuel filter with no change.
What can it be????