need help please!
 

good day to all, i have a 99 grand marquise it has been miss firing for a few days now, i took it to autozone and had the codes pulled, it has 3 codes one for a miss fire on the number 4 piston one for insufficient egr flow and one for evap control system large leak (0.080") detected. so i found a web site that walks you through testing of the egr egr solenoid and another component attached to the egr they all passed the vac test and electrical tests any ideas where i should go from hear or what i missed? p.s. i have replaced all spark plugs and coil packs it still miss fired so i put a coil that i knew was firing from the other side and still it misses

Attack the codes in the order that they appeared on the scanner:
RE-set the the codes after each item is corrected.
The "Insufficient EGR Flow" is USUALLY fixed easily by removing the EGR Valve and scraping out the carbon that has built up in the internal passage.
Messing with the TUBE that goes from the EGR valve to the exhaust manifold was NOT necesssary, although it is often recommended by various "mechanics".
The carbon builds up between the valve and the flange that the valve is mounted on.
There is a metal gasket between the valve and the flange -- if the EGR valve passes the vacuum test, BE CAREFUL to save the gasket.
With the carbon removed from the EGR valve and the flange side, clean all surfaces and re-mount the EGR valve.
When I did the job, I replaced the DPFE sensor with a newer type that isn't as heat-sensitive as the OEM sensor.
Before working on the EGR valve, REMOVE the windshield-wiper housing that goes across the cowl -- you'll save A LOT of time and hassle, and you'll be able to see and reach the components much easier.
You say you replaced the spark plugs -- I hope you didn't apply ANY type of anti-sieze compound to the plug threads -- it's a SERIOUS NO-NO, because it can "short" the plug gap and allow a mis-fire.
Do yourself a BIG favor by getting a Code Scanner of your own -- you'll save money in the long run, and learn a lot at tyhe same time.
As for the Evap System leak, you'll have to inspect the lines and fittings all the way from the Gas Tank to the Cannister.
Good Luck !!