T&A movie I saw about swing parties at a drive-in in 1978 or 79

I saw a T and A type movie at a drive-in in 1978 or 79. It was about a guy who had trouble pleasing his wife due to premature climax. She was beautiful but a demure proper housewife type.

His friends tell him about swinger parties they attend and he's interested. He talks to his wife about it but she is very opposed. But after another disappointing lovemaking session with her husband, she warms to the idea.

They get to the party and he promptly hooks up with another woman but can't perform...he's frustrated seeing his wife enjoy himself with another man. His wife turns into an absolute beast and has a GREAT time and insists on going to these parties regularly in the future. Naturally this infuriates him

He takes out his anger by killing all the men who had sex with his wife. One he traps inside a car and then feeds an exhaust hose into the passenger compartment. Another one he kills with a sniper rifle while the victim is swimming with his wife...and btw he kills is friend's wife as well since she also had sex with his wife.

I cannot recall how it ends but I am VERY certain of the details I have given.

Can anyone help?

Thanks in advance

I've seen this.
I'm trying to remember the title. I think it's Swinger's Party Massacre. Let me check my letterboxd diary.

https://letterboxd.com/film/swingers-massacre/


Swingers Massacre


While googling I think I saw, "Inside Amy," pop up as an alternate title.

ETA: admittedly, I'm not remembering the details of the kills, but I do seem to recall one of the women at the swingers party was also on the kill list, so I'm assuming it's this and not a very, very similar movie. I remember in the opening, you find out the male protagonist has some job that required him to be called to a crime scene of a murder that basically served as a bookend for how the movie ends.