Im pretty sure that Staind doesn't use a 7-string, but This version sounds close.
Intro:
D|--------------------------------------------|
A|--------------------------------------------|
F|--------------------------------------------|
C|--------------------------------------------|
G|--8-8-8-8-8-8-8-----------------------------|
D|--8-8-8-8-8-8-8-----------------------------|
A|--6-6-6-6-6-6-6-----------------------------|
pm . . .
[ Tab from: https://www.guitartabs.cc/tabs/s/staind/suffocate_tab_ver_3.html ]
First Riff:
D|--------------------------------------------|
A|--------------------------------------------|
F|--------------------------------------------|
C|--------------------------------------------|
G|--8-88-888--8/9-----------------------------|
D|--8-88-888--8/9-----------------------------|
A|--6-66-666--6/7-----------------------------|
pm .......
Chorus:
D|-----------------|---------------------------|
A|-----------------|---------------------------|
F|-----------------|---9-/11\9-/11\9/11\9------|
C|---9--7----------|---------------------------|
G|---9--7---7-8----|---------------------------|
D|---7--5---7-8----|---------------------------|
A|----------5-6----|---------------------------|
Outro / Other Riff:
D|------------------------------------------|
A|------------------------------------------|
F|------------------------------------------|
C|--10---7----------------------------------|
G|--x----x---8------------------------------|
D|--8----5---8------------------------------|
A|-----------6------------------------------|
