highway cruise stumble

[Sethyboy85]

driving between 65 and 80 miles per hour the car has a stumble that I cannot figure out. I change the plugs from some NGK to Autolite 64 but that does not change anything. if I bring it in to boost the stumble goes away Imediately and sometimes back as soon as I go back to vacuum. it almost feels like a dying fuel pUmp but going to boost it runs smooth so that kind of make that not possible

91 spirit rt
Fwd stg2
+20's

[Sethyboy85]

Update, made it to my destination but it started stumbling at slower speeds so maybe my fuel pump is going. When it would stumble the OTC read very low 02 v. Could of been my timing to look at it as you know that sensor bounces all around except for wot.

[Black93RT]

Update, made it to my destination but it started stumbling at slower speeds so maybe my fuel pump is going. When it would stumble the OTC read very low 02 v. Could of been my timing to look at it as you know that sensor bounces all around except for wot.


One possibility is head gasket between 2 cylinders, long time ago my R/T did that and I had a highway miss and it was losing coolant (but it was going out the exhaust).