Shaking over 65 mph- what is this

My car starts to shake over 65 mph. I recently changed 2 of the fuel injectors. Before I change it, it was shaking more vigorously and at all speeds. Now it only shakes at higher speeds and moderately. But it makes me feel very uncomfortable. I am thinking that tires can be problem. Can the tire alignment be the problem? or can the air pressure be a reason? Please help...

thank you,

Burak

maybe it's the other 4 injectors...

maybe it's the other 4 injectors...

is there a possibility that they are from tires or alignment

could be, I suppose, I'm just pointing out the obvious

Do you feel the shake in the steering wheel, the seat or from the engine??

Do you feel the shake in the steering wheel, the seat or from the engine??
I think it is coming from the wheel and driving seat. But it is not a vigorous shaking. I dont feel it is coming from engine (not like it was before I changed 2 injectors)

check out the turbines on your supercharger

try rotating you tires, swap them from front to rear

I have the same problem. It smooths out at about 70. I had real good luck with this same problem on a Volvo. Dealer could not figure it out. Had it for years. Then I found a guy who had a GSP 9700 computerized tire balancing machine. It match balances you tires. Volvo started riding like it was new. I plan on taking the Riv back to the same guy.

http://209.176.154.132/pub/search/findgsp9700.cfm