3.4 intake gasket

99 Pontiac Montana 3.4 with 118,000. Replaced the intake gasket due to leaking. Also replaced spark plugs thermostat, hoses and changed the oil, etc. While it was apart. Went together fine, started up and ran great with no noises or leaks of any kind. Drove it about about 10 miles that night. On the way to work the next day it drove great for about another 10 miles then suddenly it started missing badly and making a ticking noise. The noise sounds like upper valvetrain from the rear bank. It increases with engine speed, and the van has no power at all. It acts just like a mis-fire.
update: I hooked up a scanner to read codes, and there is no power at the DLC connector. Any ideas where to look for a cause like this? Thanks!

Thanks for the reply! I could not locate a bad fuse to the DLC, so decided to use a jumper wire with a 5amp fuse and backprobe the connector to supply 12v. It worked-powered up the scanner, read code (#2 cyl mis-fire). Problem was loose rocker arm. Re-torqued and all is running well so far. I was not able to pinpoint the noise from the stethlescope, but pulling the plug out to see it was fouled verified the cyliner location.