[Old Guy with 87 GT]

yes there was remnants of oil on the plugs .......the plugs were dry for the most part but the was a little oil on the threads of two of em

the tell tale sign was burnt oil smell at wide open throttle ..........i couldn't see oil burning or blue smoke....... the exaust had kinda a funky smell and you could tell it wasn't tuning it self right .........i knew it was burning oil from a friend telling me he smelled it when he was behind me every time i opened it up

i kinda knew to look for this problem cause it didn't burn oil before i did my intake swap and it was the only thing i could think of that woulda fit the symptoms i was having
(another symptom was when tuning ,it acted like it had a vacuum leak , but i couldn't find any vacuum leaks)

on another note ......the tell tale sign of oil getting by the valve seals is smoke at start up .............if you seals are bad what happens is when you shut the moter down oil runs down the valve and builds up in the cylinder .......when you start up the car it burns off that build up letting out a small blue smoke cloud till the exess burns off