stryker 490 hp problems

I have a stryker 490 that has been gone through and is peaked and tuned that I have not used in a years. I just reinstalled it again in my pick up truck and it keeps blowing fuses. I checked the wiring and all is fine there. It's hooked to a firestick with 18 feet of coax that has a solid ground. I started with a 2amp fuse blow it moved to 4 amp and an 8amp with all the same results. Not sure how big of a fuse it needs and kind a worried about putting to big of one in there and destroying my radio. Also it only blows the fuses when I try to key up with an 8 amp fuses it made it about 2 seconds before it blew. Everything works in till I keep up. Even with the power turn all the way down it still blows them. I would really appreciate any help with this. Thanks