5.0 f150 ( old engine had 87000km) Got a new block installed (warranty) due to bad exhaust valves and 200km down the road engine light and code P0300 comes up on acceleration. taking it back asap as warranty expires in 10 days. i don't want to have to pay for unnecessary diagnostic tests as the root of the old misfire problems were fixed . could this be a installation issue or coincidence that a coil or fuel injector issue just happen to come up? i really don't trust them after how hard it was to get a compression test on the old block without paying for a tune up act. also engine seems to run fine now maybe a 100rpm rough idle sometimes.