You need to check to find out. A timing light would tell you if the distributor is timed correctly but even if the distributor is timed out slightly, it should not affect no load full throttle by too much.
If the timing light shows the ignition timing is outyt by too much and cannot be timed correctly, the problem would be timing belt installed out of timed. Even if the ignition timing is correct, the timing could still be installed out of time if the other cam is not synchronised with the belt.
The other thing to check would be clogged exhaust system and fuel pressure/delivery.
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Sunday, July 21st, 2013 AT 6:26 PM