Issue With 96 Lincoln Continental

I just bought a 96 Lincoln Continental. There are a few issues I need help with.. First, the guy I bought it from said he would get the SES light out.. Well after 1300.00 he could not get it to go out.. The codes were P0171, p0174 , Both BANKS LEAN.. They did an intake manifold and MAF sensor.. Finally he took it to the Dealer who said, IRMC assemblies..He wanted 3200 for the car, it is pretty nice, but lowered it to 2000.00 because WE CANNOT get those Discontinued PARTS!!. So, we reset the light and it has been off for 2000 miles.. MY argument is that if these Parts are bad, this is MECHANICAL, the light would come back on RIGHT AWAY!! We tried the starter fluid and on one or two occasions the idle stumbled but did NOT go faster. But this test does NOT work all the time. Spraying starter fluid all around the engine area and around the IMRC shafts..The other issue is when the car comes up to operating tempuratures, the cars 2-3 shift will go into a no shift like going into neutral. Let off on the gas and it goes into gear.. This happens maybe 2 times out of 100 2-3 shifts.. Could these two problems be related?? For example, a speed sensor, or a vacuume line at the transmission.. Thanks in advance....

If it works ,don't fix it!
2000 miles / No code, it looks like the lean problem is resolved.
During the drive cycle,if at fault, a DTC would of been thrown.

CAUTION - Starting FLuid canbe very dangerous when looking for unmeter Air leaks!

How many miles are on this car?
Does the Engine run GOOD?

Note:
A misfire can make a Transmission look bad!

Focus on Transmission problem.
1) Change filter/oil in tranmisssion.

MCGIVER

164000 and yes it runs VERy GOOD... DOES NOT use oil...