All you changed was the intake?
Check to verify you plug wires are connected correctly. It should be 1-8-4-3-6-5-7-2. Typically looking into the engine bay the two plug connectors post on the cap are close to parallel to the front of the truck, the one on the left (passenger side) is #1, the one on the right (drivers) is #2. To use the timing light, connect the positive and negative to the battery and the spark lead to the #1 plug wire. Point that down to the timing mark on the harmonic balancer and find the timing mark and the number it is located. Typically you need about 8-10 degrees initial timing (disconnect the advance hose) Rotate the distributor to get it to that point.
Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project