92 tbird won't start

My son has a 92 tbird LX with 5.0 engine (140K miles). It was running then starting to lose power. When he pulled it over to the side of the road it would not restart.
After towing it home I have done the following:
Checked the engine error codes (I only get 114 & 116)
Replaced the fuel filter, checked the fuel pressure (40 psi)
Cranked the engine with a plug out to check for spark (had a good blue spark)
Replaced the spark plugs and replaced the battery
Checked the injectors to ensure they were getting voltage (I get 12V on the red wire and the white whire voltage varies like it is getting a signal when cranking)
Checked the trottle position sensor and it had a varying resistance based on throttle position

When I crank on it it will crank at first then loses steam quickly. I am concerned the timing chain has slipped. Is there a good way to test for this without removing the cover? Also any other ideas or areas to check would be appreciated.