few things that bug me after engine swap

[arsenicpants]

I recently swapped in a turbo 1.6 into my mk1 jetta and there's a few things that i feel are really weird
if anyone can give me some help on any of these you'll be saving me from going balder faster

1. at low RPM (like idle), after decelerating, the RPM will stay up slightly for a few seconds, then suddenly drop to normal RPM
this is with the engine out of gear and coasting, or sitting, or whatever
it doesn't do it 100% of the time, but more often than not
i have no idea what's going on here
i think it has something to do with my LDA, and that it's overcompensating for the turbo, but I can't figure it out

when it does drop it sounds like there's some kind of rattle or vibration
it's really hard to explain, i might just have to make a video or something

this problem only surfaced today after increasing my boost pressure through my k14's wastegate, and increasing the max fuel screw

2. engine shutters & bucks at low RPM when accelerating from a moving idle, or when decelerating and then giving a slight bit of gas at low RPM. giving it a bit of clutch or bringing it out of gear will make it go away
i think think this may be because of my transmission's differential
any ideas?
because of the erratic idle of problem #1, the shutter is worse

3. engine WILL NOT push the car faster than 120 Km/h. and if car has been running for a while it will have trouble even going 100 (and really, it's not even that fast, my speedo is way off). I was told this had to do with a boost leak I had, but the leak has been fixed and it still won't go faster overall, it's just slightly faster in accelerating, and 4th gear can go a little farther
clutch is not slipping. could this also have to do with my transmission's differential being lousy?
transmission is a 7A (3.94 FD, 3.45, 1.94, 1.29, 0.91, 0.71)

if anyone can give me any ideas, i'd be grateful

[8v-of-fury]

a 7A behind a 1.6TD should and will go faster then 120km/h

I have an FF (3.89 FD, 3.45, 1.94, 1.29, 0.91, 0.71) behind a 1.6 N/A and I can easily do 120km/h. 145km/h if I push it (top speed btw lol)

Something else has to be WAY OFF. Not enough fuel, not enough boost something! Does it blow black on a WOT pull in 3rd? any smoke at all ever?

[RadoTD]

Problem one I'm pretty sure I know the answer to. It has to do with the whole "fuel map" being shifted up by adjusting the max fuel screw and it not dropping to idle properly. It's easy to explain in person... are you going to Great Canadian? I can show you then or I noticed you mentioned going to some of the Coquitlam meets on Dubberz, I'm out to most of those and I can show you what you need to do. If you're stopped at a light and it's sitting high, dragging the clutch in gear should bring it back down and it'll usually stay there.

2 and 3 I'm not too sure about.... maybe try to explain them if I end up running into you

[gldgti]

do a compression test, and check the amount of blowby you are getting..... could be broken/worn rings. i have had vw diesels act pretty oddly and poorly because of too much blowby gas... and then you get runaway.

[Baron VonZeppelin]

I agree with Rado on #1.

#2 sounds like an internal pump problem.
Which could be from fuel restriction (lines/hoses/filter) - low internal pressure - or governor quirks.

#3 what speeds would the car attain with its previous engine ?
That isn't a total crap tranny. Its under 3.00 final drive range which is fairly diesel friendly.

Some possibilities are bad flange bearings on tranny or terrible front end alignment or dragging brakes or full throttle governor is low or throttle cable is slack.

[arsenicpants]

Thanks for the help guys
RadoTD, sorry i didn't catch you at the show, I saw you're car but don't think i've met you before so i didn't know who to look for, hehe
i cut the max fuel screw back a degree or two and it no longer does the weird idle thing
it's got less oomph now though, of course

the low speed shutter happened before i did the swap, and the transmission is the only thing that's the same from before, which is why i think that's the problem
the car did about the same top speed before the swap as well
the previous owner, and engine builder, said he'd have no problem keeping 140 km/h on long uphill climbs in his old rabbit