as fasteddy said,,,retorq heads.
Did you use silicone at the ends od you manifold gaskets. I've had slow leaks there , just enough so you smell it but don't see it cause silicone sealant wasn't used.

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.