weird oil bun out of exhaust after auto tranny fluid change!!!

[FIBA M - EC17PSE]

So yesterday I did an auto tranny and filter change on my 97 gst! And it was all good and went smooth! But here's the part I'm a tad worried about once I put about 3 quarts in I ran the car like I'm ment to and check the levels and topped up from there etc etc the car was running for about 25 mins while I checked it and ran it warm to check the hot levels. Then I turned it off and upon restarting it and driving down the road there was blueish smoke coming out the rear??? Now I did a compression test a few months ago and that was good all about the same but I'm going to do it again aswell just to see what the results are. I then took it for a longer drive and it never smoked after that? So I'm a little lost as to what to think of this? I have a small oil leak down by the timing area but its so small it can wait till the timing is done as its not causing any problems just yet!

So what do you all think could of caused it or why?

I thought maybe as it was on idle for so long it didn't like it.
Also I didn't know where to put this as its not just tranny but engine aswell so feel free to move it if needs be.

Thanks all

 

[DSM1G90]

Valve seals .. end of story.

 

[FIBA M - EC17PSE]

Valve seals .. end of story.

I thought this but wouldn't it do it a lot if they were gone/going? It's probably the 3rd time its done it in just over a year1 so its strange and that's why I thought it was just a little hiccup .

If it is the valve seals can they be changed without lifting the head?? And just the valve cover? As its never had a head gasket and they charge loads of money to skim heads over here in the UK!!

So anyone can I change the valve seals with the head on!