Like they said your timing was off.
And the gaskets well you gotta do the correct torque sequence and proper force. Also a good idea to re-torque them after a couple of little heat cycles.
2014 V6 Deep Impact Blue Mustang 2.73 (Uughh)
1989 Sonic Blue Mustang LX Coupe, 349 ci, TW heads, TFS Track Heat intake, 75mm Accufab TB, 80mm ProM, 30 lb inj., Jay Allen cam, TKO, 3.73, 31 spline w/ TruTrac, MAC 1-5/8" LT headers w/ h-pipe, 2-1/2 flowmaster, electric fan, Moates QH
392 rwhp 424 rwtq....Mustang Dyno
"There are three kinds of men. The one that learns by reading. The few who learn by observation. The rest of them have to pee on the electric fence for themselves." -Will Rogers-